goggogaowsm: On the topic of Air galleys actually, it reminds me of a strange phenomenon. Started a few new maps with my brother, this time on MPE so I could do battles (him getting a new laptop meant he could do battles on v1.4, but I still couldn't, was very strange). For some reason, we found we were able to just continue our pre existing levels on MPE as well, even thought they were many turns in and had started from 1.4. It meant any already existing units, would be given their MPE abilities, but still keep 1.4 abilities (new units just had MPE abilities).
Which meant Dread Reapers still had regeneration, but if gold medal would also get animate corpse. And the weirdest one was Air Galleys, they would still have two lots of 3/3 shoot javelin, but also had fire cannon and fire crossbow, so basically could shoot 12 times in a battle.
Unit abilities are generated by the current ruleset, but they are also stored in the savegame. So a unit will have all the abilities accorded to them under the ruleset at the time of their creation, plus all the abilities accorded to them by the current ruleset. Newly created units won't have abilities from a ruleset which was used only before their spawning.
I noticed this first with MPE mods years back, but really understood it once I accidentally started a PBEM under my own mod, and surprised people when they came across indie Spirit Puppets which had Invoke Death. Mod had some rougher edges back then, I've made them less zany since...
By starting a map under a custom ruleset, then immediately switching to whatever is to be played on, you can alter the abilities of pre-placed units. Did you want a special city guarded by independent knights which are pjhysically immune and have Divine Breath? You can do that! Another fun thing you could do, is give everyone a single starting unit which is immune to all damage, as long as it doesn't have an attack under either ruleset. Like say a Rebuilder with all immunities, then everyone would have a special chess piece which can block off map hexes. Would be interesting!