Projected feasibility: 4/10
Impact: Probably not very lore friendly but I really think it could be fun and create some dynamic replayability between friends.
Detailed description: I'm imagining a PvP mode where both players choose various locations for important facilities and troops similar to the challenge mode, and once both players are ready they race against each other trying to take out enemy positions fighting against the clock also like in challenge mode which will then expose the enemy nest position to destroy and win.
I think getting this to work multiplayer could be relatively simple, it would just be sharing a version of the world map, various unit positions and enemy shot locations between clients.
It's quite the long shot which is why I decided on the feasibility being quite low but it's just a fun idea for later down the line.