Maxperson
Morkus from Orkus
If you look at the Speed Factor rules, it says "everyone rolls initiative" and "on its turn a creature..." That would seem to allow individual monster initiatives. It also says, "Under this variant, the participants in a battle roll initiative each round. Before rolling, each character or monster must choose an action."Actually, individual initiative isn't even a variant. That's right, check the DMG. I thought it would be there too but there's nothing saying you can RAW do identical creatures with separate initiatives. It's actually more of a house rule than automatic success ability checks and injury tables since the books at least provide those two as variants.
As it's an optional rule, it replaces the rule in the PHB and says nothing about rolling all monsters of the same type together.