Spawning more weak enemies means a lot more ammo drops during missions–provided nothing else about them changes. That’s fine by me, since one of the hardest things about playing on very hard difficulty is constantly running out of ammo during boss fights and having to ‘take a break’ while I farm mooks for more. It’s understandably pace shattering …
That said, this will probably get annoying on missions where mooks keep spawning until a key target is down or an objective is fulfilled. Sometimes I like to kill off all the mooks and fight just the strong leftovers, but if the mooks keep showing up constantly that won’t be a thing anymore.
As for certain enemies engaging with players in more than just a chase, stop, attack, pattern, you could have enemies that just plain refuse to commit to the fight until certain conditions are met. EG: The player’s health is really low, they’re using a long range or melee weapons (binary selection to match enemy’s strengths), or that enemy (or their type of enemy) is the only one left on the field. Those are all the spitballs I’ve got for that right now, though.