How about creating Deatchmatch mod? It must follow these rules:
- No killing inside bases. If we kill somebody inside base, we don't get or just lost point. Player, who returns to base(not spawn) can be killed.
- There no stages(player will get maximum stage) or player works to new stage by themselves. It's not team play.
- Each player can also build some buildings, but outside a base. There a matter with aliens - only specify units can build. Humans can carried construction kit. Each player will get own construction point and can't build reactor/overmind - he don't need it.
- Credits are lost after player dead, so better spend credits as soon as possible.