We SERIOUSLY should think of just adding another difficulty level here.
The reason: Putting the health pickups back up to 2 is going to wreck what difficulty is there; the attrition is the entirity of what keeps it this way. Every single game in the genre that actually has challenge to it does this. Isaac doesnt, which is a huge part of why it's too easy.
However, with Normal likely becoming another "dont have to try", which is what would happen (no need to avoid damage when it's that easy to heal), that means the only other option is Hard for those actually looking for something more interesting, and that's a big jump up. Hard mode is intended for those that have completely mastered normal mode.... when normal mode is putting up a fight. Which would effectively mean that, with the change, Hard mode would be for those that have mastered a totally non-existent difficulty that comes between normal and hard. And no, I'm not re-balancing Hard mode. The ONLY way to do that is to completely restructure.... everything. ALL of the patterns. All of them. It's not stats that drives that mode.
Also, one other major reason: Switching something like that core mechanic between difficulty modes is a very bad design choice, and usually seen as artificial difficulty. Enemy stats are one thing, but changing the nature of a basic pickup is bad. In other words, as far as I"m concerned, this one's a definite no-no here. The player is taught from the beginning that a health pickup heals for a specific amount. Just deciding "sorry, nope, it does this now" when going up a notch is not a good move. Remember how enemy damage was multiplying on higher difficulties, and how much of a mess THAT was? It's a similar thing here.
And one way or another, this game was never supposed to be a zone-out sort of thing to begin with. That's been a huge reason for all of these changes to begin with. Something like Isaac is alot better for that. The only reason this game was like that is because it was broken. We need to not forget this when making changes here.
This all makes me think of 20XX actually. Where the default mode, in which everything does 1 damage and healing is equal to that, is considered simply too easy. Much too easy. But make ONE change... double the damage enemies deal (effectively creating the attrition effect, because healing no longer keeps up if you're tanking too much) and the game's challenge rises dramatically. And that's the ONLY change you need to make. No other difficulty options even need to be set to produce that effect.
That's how strong of an effect this sort of thing has on any game in this genre. It doesnt matter how dangerous enemies or bosses are: If it's too easy to heal, the player doesnt have much effort needed. Which also means that everything in the game seems less important/meaningful. Been trying to avoid this since the start.
If you must put the HP things up again, do it only on easy and below.
Now, none of this is to say that we cant tweak Normal mode AT ALL. But this is absolutely the wrong way to do it.
And like I'd said elsewhere: We shouldnt make huge changes until the rooms are dealt with. I guarantee you, the room issue is a huge cause of the difficulty being warped on normal. Fix that, and rooms are less congested and it's not as ridiculous for the player (whereas hard mode wont get hit as much by that, because enemies will pump out lots of crap anyway). I seriously cant emphasize enough how important this room thing is for the game's balance and such.