I can't quite figure out why these monsters can use weapons and medkits. They couldn't use either in Doom. Why would a medkit heal a demon, and how would they even be able to apply it?
If the goal is to make Barons and Knights more of a threat, this doesn't really accomplish it, at least in my opinion. It merely makes them more irritating (I get quite irritated when I see a large medkit go to waste). Sure, when they heal themselves they are tougher, but nothing is more of a pushover than a Baron or Knight with a pistol or shotgun. I think the final score is a wash, with the edge going to aggravation. If your goal is to make them tougher, perhaps a straight statistical upgrade is more consistent.
On a side note, you may want to consider extending the 'medkits can't be picked up on level 1' beyond ITYTD, at least to HNTR. Perhaps it isn't in the spirit of the game, but neither is quit/restarting until you get a favorable clear + 4 medkits, which for me at least is standard operating procedure anytime I expect a tough game (so, basically every game.)