What would your opinion be on being able to use variables while also using another variable (read desc if this doesn't make sense)

what i mean by this is like using grunts whilst also being able to use grunts M. Of course, this would take up still a slot in your army, but youll have two versions of grunts.

This could also work like being able to use Riflemen and Grunts at the same time.

It could also being able to use Armed Heli while having Missile Heli as well.