Identical balls & building , assuming vacuum & ignoring terminal v altogether, one dropped and one thrown directly down at same moment, how could one theoretically achieve a simultaneous landing?
You can't. If you're imparting additional force to one of them and release both at the same point, the thrown object will will land first.
Also, if you assume you're in a vacuum, you don't need to ignore terminal velocity. There is none.
EDIT: I suppose you could do it if the ground weren't completely level, but I assume you mean all things are equal.