So my suggestion isn't so much for tree tag, but for the creation of a variant of it. What if we had two teams, Terrans and Protoss, each with some workers and thors/colossi?
The object of the exercise would be to kill the opposing teams probes/workers, who would then be sent back to a jail on the opposing teams side of the map.
It would be tree tag crossed with capture the flag. What do you think?