Since your english has some mistakes, I will rephrase the thing to be sure that I understand it right: if a player leaves the game (which can happen when th player quits or when he gets disconnected), you want to put his units under ai control?
This seems to be a nice addition to the usual options of either self-destructing or transferring to an ally. But it'll only be useful if the ai is good. If you add it, the player who leaves should decide whether ai takes control of his/her units. The ai should be about as strong as the player who leaves to keep it balanced.
But before you make an ai that takes over a players units, make a general ai. You'll need that anyways and its one step less. Yea, I'd really like to see a general ai.