Races in New Battle screen are hardcoded (because they're not all implemented
), so you'd have to add them in there manually.
There are 3 things a new "alien race" needs in the ruleset:
- The "unit" entry, which defines the unit stats, behavior, etc.
- The "armor" entry, which defines the matching armor and drawing routine.
- The "alienRaces" entry, which defines the crew layouts for each race (these are already done, but you'll have to remove unimplemented units to test it).
You can probably just copy-paste an existing unit and edit it accordingly.