I haven't looked at the command engine or played with it much, and I'm not sure I understand your point.
Still, here's what I know:
"player" is a reserved variable that returns the unit that the player is in. In a multiplayer game, the value of "player" will vary from FE to FE. Figuring out who the player is playing is pretty easy though. So I suppose you could have a userinit that set up say eight command arrays, as well as:
playercommanders = [grunt1, grunt2, grunt3, grunt4 ... grunt8]
then you'd just find the position of the player in the array (= which person the player is playing), and assign the commandable units to him.
It sounds like Spinor's script is using the "Usermarker" script for commands (click on map, set up marker -- units go to marker). If that's true, then it will not work in a MP environment, as MP markers are numbered differently.
You could, of course, replace the usermarker script with a clunkier system like the one I have for artillery (enter in a six-digit grid location using the action menu, or laze the location). Or you could get resistance and create a dialogue to accomplish the same thing using mouse menus. Then it would work in MP, and you could have each player command several squads.
As for maps -- check out the WRPedit section of OFPEC's forums. Phaeden is making a map with some decent-looking military bases on them (and urban combat training zones, etc). The screenshots look promising.