I have Roma Surrectum 2.5, Rome: Total War on Steam, and I can get all this to work:

Default Factions 1 Turn (Except Rome)
Default Factions 0 Turn + Rome
Swap Factions 0 Turn

What do I need to write in the Launch Options in Steam in order to play 1 Turn campaigns with both Rome and the Swap Factions.

Thanks in advance