Changing the mark of a ship isn't really possible; it would have to be removed from the game and replaced with a new ship of the different mark (that's how reclamation and giving work, too). Not really interested in opening that can of bugs.
Making it use the normal regen logic with health adjusted according to mark difference would be possible, but isn't really what I'm looking for because of the cases where stuff being regen'd has more max health than a goat. Also, I'm leery of possible exploits if a goat isn't a one-shot thing, due to repairing and whatnot.
The two ideas that seem to work to me are:
1) Bite the bullet on the not-one-shot thing and make it so that:
- an X-mark goat regen'ing a Y-mark ship loses (Y/X)% of its max health.
- goats cannot be repaired
- give goats a slow (say, 60 second or 120 second) self-regen so you don't have to manually scrap damaged ones to maintain cap-effectivenesss
or
2) Make MkII goats have exactly the same stats (including costs) as MkI goats, but with 2x the cap, MkIII have same stats but 3x the cap, etc.
- This seems the cleanest approach to making the higher marks more useful in the key role, though a bit unconventional and on high caps that gets to be an awfullotta goats. But it seems preferable to the other solutions I've considered.