I think the question would be: why are you interested in heavy armor proficiency? Typically, it's because you want your character to be tough and defensive. Hey presto, this does that.
I also imagine there's multiple feats that would grant that proficiency. Maybe a Defender feat grants heavy armor proficiency and gives you the ability to take damage for allies. Maybe a Swift Slayer feat gives you a movement boost, plus the heavy weapon proficiency.
What is the goal you had in mind when deciding you wanted that proficiency? The feat can now support all of that goal at once, instead of requiring a series of minor choices.
The thing is, the number of possible reasons that someone could have to want proficiency in heavy armour (or any similar game element) is—pretty much inevitably—going to be higher than the available number of feats that grant that game element as one of their components. I mean, unless we're expecting to fill up entire books with heavy armour proficiency feats with varying additional bonuses.
There's no way for [Heavy Armour Proficiency,X,Y] feats to ever be as flexible an option as [Heavy Armour Proficiency], [X], and [Y] feats. You'd have to offer dozens of variations to keep up, which in the end would simply be the same as offering the benefits as separate elements … only taking a lot more words and pages to do the job.
People have complained before about this class or that carrying unwanted baggage. This approach means that inevitably we'll have
feats with unwanted baggage. People will want two out of three elements, or one out of three elements, and have to take the unwanted ones as well just to get them. Your multiple-feats-grant-the-same-thing approach seems destined to cause far more feat-bloat than either 3E or 4E ever suffered from, because those systems only needed a single proficiency feat for each type of armour (or any other specific game element), whereas this approach would require multiple ones.
I mean, I just leveled up in one of my 4e games. It came with a feat. Pretty much everyone hemmed and hawed over what feat to take because none of them really mattered, but it felt like we'd be missing out unless we carefully selected the right one. This is not what you want.
I must say that my own experience in 4E is vastly different. I usually feel feat-starved (even when the majority of characters I end up playing are human, and thus get a bonus feat). You could grant my characters a feat at every level and I'd still have to pass up feats I'd like to have, feats that I feel would
matter.
The latest character I'm playing just reached level 2, and I'd say that each of his four feats (human, class bonus, level 1, and level 2) matter. Heck, every feat the character will take in heroic tier (assuming he and the campaign last that long) is already planned out, including retraining along the way.
—
When they said they'd be making feats more significant, I—perhaps foolishly—thought that meant that feats were going to have more benefit in terms of
quality, rather than more benefit
s in terms of
quantity. 'Feat X grants you benefit y' being replaced by 'Feat X grants you
Benefit Y!'. Instead, they seem to be going for 'Feat X grants you benefit y, benefit z, and a side of fries' … whether you wanted fries with that or not.