Please respond its for my brand new rpg

Not in any conventional way

I think in Starcraft 2 Coop mode, they got that effect for the Omega Nydus Worm by creating an unit for the player other than the main controller that overlap with the original nydus worm, each player clicking its own version of the unit.
Rather than a solution, it may be a lead to one.

There is a mode in BW that lets 4 players control the same units (Team Melee I think its called) but IDK if it can ever work with UMS. Maybe with EUDs?

Unfortunately you can only truly do this in team melee, not UMS. I'm no expert on EUDs but I believe you could give the unit to whichever player is currently selecting it using them, but you can't have players control the same unit simultaneously.