Some feats such as Actor and Keen Mind provide a single Ability Score increase along with some other benefits. These feats are sometimes called half-feats (and I am using this definition for this question).
Half-feats are sometimes difficult to incorporate into a build unless you plan ahead and even then you probably need to spend at least part of your adventuring career with an odd Ability Score.
In order to somewhat ease taking these feats, I was considering including this house rule in a campaign:
When you would gain a single feat, you can instead gain two half-feats but do not receive their Ability Score Increases. This counts as taking both feats for the purpose of being able to only take each feat once.
At first glance, this seems naturally balanced because the non ability score benefits of a half-feat seem to be equivalent to a single Ability Score Increase, meaning you are still obtaining the "value" of two Ability Score Increases.
One difference I notice is that this is a bit better for half-feats where the Ability Score improved is fixed (such as CHA for Actor). If you spend 1 ASI on 2 half-feats and then spend the next ASI to increase two ability scores, you've effectively taken two half-feats but gained the ability to reassign their associated ability score increases however you like1. I am okay with this benefit.
Am I overlooking any other benefits or balance issues that this house rule might introduce?
1. As written by Ryan Thompson who helped clarify this in comments.
Best Answer
Generally, this should be fine, but is strong.
You're speeding up the rate at which characters can get certain features and allow them to really spread out their utility.
A Warlock could get up to heavy armor at level 4 (level 1 with a variant human) by taking the half feats for moderately armored and heavily armored (which could be countered by not allowing prerequisite half feats to be paired).
A Dragonborn could get both Dragon Fear and Dragon Hide benefits, should they desire.
It's hard to quantitatively compare the utility effects of two of these "half feats" vs just a +1.
Watch out for Fighters and Rogues
Fighters get enough ASIs that they could max out their primary stat and then get 10 half feats; Rogues could do 8 half feats. Again, it's hard to say what mechanical effect that would have and I'm not sure why someone would go for that, but there it is.
Fighter with 8 half feats:
Addendum: Racial Feats