@deribus This should be extremely easy to set up
You could create a test version with a SIM mod that you would use with "Supremacy" or "Annihilation" game modes (either one would work the same)
The test mod would basically do the following:
Every so often, test if the team has any ACUs left. If not, exterminate all units belonging to that team. Once all the units are dead, the in-game logic for "annihilation" or "supremacy" mode should trigger a victory (or, if applicable, a draw).
"Every so often" would probably mean (1) every time an ACU dies and (2) every 5 seconds, just in case for some reason the game logic misses that the last ACU died, so you don't have a game that drags on incorrectly.
There are LUA coders in this community who could probably make that mod in literally less than 10 minutes.
I don't know how much extra effort it would take to add that as a standalone game mode alongside "Assassination" "Annihilation" etc. but that's not even something to worry about until you've had a chance to test whether people enjoy playing it. If you made it into a standalone game mode, you could enable those matches to be ranked of course.