Hey see the answer here
The only thing you can host right now is a lobby. But you need to give the address for people to connect to it.
https://github.com/0ad/lobby-bots
Sounds like a very complex feature with lots of edge cases. I can imagine units defecting to gaia as a start. Else you'd need to add new players and pretty sure that won't work if you reach 8 players.
The paths are the same for all versions of 0 A.D. and in the same folders for 7 8 8.1 10 & 11.
Logs are in %AppData%/0ad/logs
Default installation path is %localappdata%/0 A.D. Alpha/
Mind the space.