Esker
Hero
Second Chance. If you miss with a melee attack, you can use your bonus action to make a second melee attack.
I mean that's almost identical to granting advantage. In some ways it's actually better, since you might already have advantage, in which case now you can use your bonus action to roll four dice. I guess the way it's worse is you can't use it to remove disadvantage, which rogues especially hate. (You probably want to call it something different, by the way, since there's a halfling racial feat called that already) I'd definitely take it, though.
Careful Strike. You can use your bonus action to add your DEX (or maybe INT?) modifier to damage with your weapon attacks until the end of your turn.
So this is basically giving them back what finesse already does, but making them use a bonus action to get the benefit? Eh.
What about something like:
Disarm: When you hit a creature with a melee weapon attack, you can use a bonus action to attempt to cause the creature to drop one item of your choice that it is holding. Make a Dexterity (Sleight of Hand) check contested by the creature's athletics or acrobatics (their choice). If you succeed, the creature drops the item at its feet.
Well, the rogue only put in one ASI for STR (while the fighter did two) so the rogue will be benefiting to DEX or getting a feat or something else, and even without it would still only one point behind the much stronger fighter.
Yeah, but the fighter is going to put ASIs in strength anyway. Nobody in their right mind puts a precious ASI into a stat they don't use for anything except one kind of skill check.
And at this point consider what you would be looking at: one of the strongest poeople in the world, skilled at climbing, against another who has only average physical strength, skill at climbing, and some additional expertise.
It seems like you're focused on the fiction, whereas I'm focused on the game balance. What you're saying makes sense in simulationist terms, but in game terms, you're taking a distinctive feature away from a class, which is already perceived by most people as a bit on the weakish side, mechanically.
I suppose one way to look at is this: I am fine with ability score matching expertise. This would allow a rogue with no great strength enough skill to match an equally proficient super-strong character. That is why our current +5 max ability and +4 max expertise is close enough I am fine with it. With proficiency max at +8, expertise can still add an edge but not overwhelmingly so.
I mean, this is exactly what RAW does: expertise eventually adds +6, which is the gap between the lowest possible ability modifier (assuming standard generation methods) and the highest.
Well, with a 90% chance to not even allow the oni a chance to detect him, he is nearly always succeeding. Even if the oni is active and it is a contested roll, he still has over 80% chance of success, which is pretty darn good IMO.
Yes, it's good. It should be good! The rogue is an expert at sneaking around, having devoted a precious resource to getting that 80-90% chance of success (or more precisely, getting that chance of a catastrophic outcome down to 10-20%)! It just doesn't feel like you (or the DM of your group) are taking seriously the idea that (a) the rogue paid a lot (in opportunity cost) for the ability to do that, and (b) for it to be worthwhile to attempt something as dangerous as sneaking alone, you want to be pretty confident you're going to succeed!
Everyone should have some chance of doing really extraordinary things IMO, not just rogues (fine... and bards).
Sure, but being able to do extraordinary things achieved via skill checks are defining for those classes. Other classes have other kinds of extraordinary things they can do.
Yeah, actually a 5th-level fighter with +9 to me IS too much. I am not a fan of the 5E mentality of hitting-more-often-and-giving-things-tons-of-hit-points.
Okay, I can understand that position, but to fix that and retain game balance would take a wholesale overhaul of the monster manual. If you're not going to do that to address the fighter's "excessive" to-hit bonus (which I assume you're not), then at least recognize (and I think you at least somewhat do) that messing with expertise upsets the game balance just as much in its sphere.