What happens in Team Monobattles if my Infestor obtains a worker of a different race?

Solution 1:

You will get to build probes, observers, SCVs and calldown MULEs. You can build every building you could ever imagine... and that is it.

The mod is built such that, all units are natively disabled until you choose the unit you want to play. So taking over an SCV will still have all military units disabled on the Terran tech tree.