(Note that while Im talking about my game below to illustrate my take on the issue, this is more about game design in general)
So what I mean by Ability Implication is the phenomenon (I call it a brain worm) that, by defining a given ability, you are implying that said ability can't be done without it.
Often I think this is just a result of defining things as abilities when they shouldn't be. Ie, Pushing a Rock shouldn't be an ability, it should just be a thing you can do regardless of who you are.
From that perspective, avoiding this issue is relatively straightforward. Abilities should either modify the thing whatever it may be, or be so self-contained that its intuitive you can't do it without it. Spells and spell-likes are rather easy to define like that; turning into an Earth Golem isn't something just anyone can just do, for example.
HOWEVER
I have also observed a rather unfortunate trend (namely in OSR circles, though it happens elsewhere for sure) where people will treat ability design in general as causing the brain worm; just by having abilities you're harming the experience, essentially, "restricting" people.
I personally think that perspective is a load of huey, particularly when considered in tandem with the first perspective; if the first is addressed then the second should have no reason to exist.
But even more than that, even with the first being an issue, if a game gives a way to take a particular action, even if its defined through explicit abilities elsewhere, it should count and there's no reason not to count it.
5e's Improvise Action, despite its non-prominance in the design is a great example of such a thing, particularly for those in OSR circles. There's nothing you can't strictly do with it short of obvious smart ass answers (I wave my sword and Cast Wish!), and if you're used to OSR style play, its really not a hassle to use and maintains the desirable freedom to just act (barring 5es rather silly Action Economy anyway, but thats a different topic).
But, this isn't about 5e so much as it is about how this brain worm can be quashed, but without just dropping abilities altogether, a solution I don't consider to count unless you're going for minimalism.
I have my own approach Ill detail separately below, but what is yours? Or perhaps the brain worm has seized control and you think this is a cursed problem? Unsolvable and undesirable to solve? The perspective is valuable, even if I dislike it.
===
The way I've been approaching this in my design is fairly comprehensive, if only for how much I intend to hammer the point home anyway.
For one, I have an Action economy that assumes and encourages the use of what I call Skill Actions, the most basic of which (and stated as such at level 0 for all 32 Skills) is in fact Improvise Action. But beyond that, Skills will have unique Actions that can be taken at any level. For example, the Tactics skill can be invoked to Analyze and opponent, revealing weaknesses and even vulnerabilities (ie, call a shot on this spot and nail it, the bug dies)
This is going to be further supported by Monster/NPC design that deemphasizes just attacking all the time (which in turn is part of why something like Tactics even exists).
For two, the way I designed Classes and Multiclassing is actually just as more elaborate Skill Trees, similar to the actual Skills, but structured like traditional classes, and with multiclassing being extremely permissive; not only is multiclassing relatively easy, but you can even take multiple subclasses. (The only caveats being that just taking a class level or two isn't the whole story; Abilities require Skill levels too for effectiveness, especially early on when investment is cheap. If you're otherwise a Mage and you try to go for some Barbarian levels, you'll be hardpressed to be useful with them)
And for three, I intend to keep Ability design cognizant of that first perspective from earlier; Abilities either modify or are Intuitively self-contained.
One example of the latter is the Barbarian's Slam!; this is a Reaction Ability that they can take, if they manage to negate an attack as part of a Defense, to immediately grapple and toss their target. Grappling and Tossing are already a part of what any character with decent Strength can do, and the key improvement the Barbarian provides is the ability to both use it Defensively as a Reaction, and the automatic success and use. Other characters with sufficient Strength can ostensibly do this, but it'd require multiple Actions to set up and do; a Barbarian can still take their actual Turn in addition to tossing the goblin off the mountain.
While one can squint and say it doesn't squash the brain worm, I think it does, as I think being able to fight like this is intuitively thematic to a Barbarian, and as noted, multiclassing is very permissive. One can in fact learn to do the ability if they invest in those abilities and the relevant Skills (they'd want high Wrestling, and thus, high Strength), and the rigmarole to do so is intuitive as well. (To take multiclass levels, you have to spend downtime to rearrange the Skill points you have earned. Your first multiclass costs 2 per level, and includes one subclass. Taking a third or a second subclass goes up to 3 per level, and it goes on in that fashion forever).
So what I mean by Ability Implication is the phenomenon (I call it a brain worm) that, by defining a given ability, you are implying that said ability can't be done without it.
Often I think this is just a result of defining things as abilities when they shouldn't be. Ie, Pushing a Rock shouldn't be an ability, it should just be a thing you can do regardless of who you are.
From that perspective, avoiding this issue is relatively straightforward. Abilities should either modify the thing whatever it may be, or be so self-contained that its intuitive you can't do it without it. Spells and spell-likes are rather easy to define like that; turning into an Earth Golem isn't something just anyone can just do, for example.
HOWEVER
I have also observed a rather unfortunate trend (namely in OSR circles, though it happens elsewhere for sure) where people will treat ability design in general as causing the brain worm; just by having abilities you're harming the experience, essentially, "restricting" people.
I personally think that perspective is a load of huey, particularly when considered in tandem with the first perspective; if the first is addressed then the second should have no reason to exist.
But even more than that, even with the first being an issue, if a game gives a way to take a particular action, even if its defined through explicit abilities elsewhere, it should count and there's no reason not to count it.
5e's Improvise Action, despite its non-prominance in the design is a great example of such a thing, particularly for those in OSR circles. There's nothing you can't strictly do with it short of obvious smart ass answers (I wave my sword and Cast Wish!), and if you're used to OSR style play, its really not a hassle to use and maintains the desirable freedom to just act (barring 5es rather silly Action Economy anyway, but thats a different topic).
But, this isn't about 5e so much as it is about how this brain worm can be quashed, but without just dropping abilities altogether, a solution I don't consider to count unless you're going for minimalism.
I have my own approach Ill detail separately below, but what is yours? Or perhaps the brain worm has seized control and you think this is a cursed problem? Unsolvable and undesirable to solve? The perspective is valuable, even if I dislike it.
===
The way I've been approaching this in my design is fairly comprehensive, if only for how much I intend to hammer the point home anyway.
For one, I have an Action economy that assumes and encourages the use of what I call Skill Actions, the most basic of which (and stated as such at level 0 for all 32 Skills) is in fact Improvise Action. But beyond that, Skills will have unique Actions that can be taken at any level. For example, the Tactics skill can be invoked to Analyze and opponent, revealing weaknesses and even vulnerabilities (ie, call a shot on this spot and nail it, the bug dies)
This is going to be further supported by Monster/NPC design that deemphasizes just attacking all the time (which in turn is part of why something like Tactics even exists).
For two, the way I designed Classes and Multiclassing is actually just as more elaborate Skill Trees, similar to the actual Skills, but structured like traditional classes, and with multiclassing being extremely permissive; not only is multiclassing relatively easy, but you can even take multiple subclasses. (The only caveats being that just taking a class level or two isn't the whole story; Abilities require Skill levels too for effectiveness, especially early on when investment is cheap. If you're otherwise a Mage and you try to go for some Barbarian levels, you'll be hardpressed to be useful with them)
And for three, I intend to keep Ability design cognizant of that first perspective from earlier; Abilities either modify or are Intuitively self-contained.
One example of the latter is the Barbarian's Slam!; this is a Reaction Ability that they can take, if they manage to negate an attack as part of a Defense, to immediately grapple and toss their target. Grappling and Tossing are already a part of what any character with decent Strength can do, and the key improvement the Barbarian provides is the ability to both use it Defensively as a Reaction, and the automatic success and use. Other characters with sufficient Strength can ostensibly do this, but it'd require multiple Actions to set up and do; a Barbarian can still take their actual Turn in addition to tossing the goblin off the mountain.
While one can squint and say it doesn't squash the brain worm, I think it does, as I think being able to fight like this is intuitively thematic to a Barbarian, and as noted, multiclassing is very permissive. One can in fact learn to do the ability if they invest in those abilities and the relevant Skills (they'd want high Wrestling, and thus, high Strength), and the rigmarole to do so is intuitive as well. (To take multiclass levels, you have to spend downtime to rearrange the Skill points you have earned. Your first multiclass costs 2 per level, and includes one subclass. Taking a third or a second subclass goes up to 3 per level, and it goes on in that fashion forever).
