* fast forward to the Sea Zone being replaced by the Annoyance Zone *
Seriously, though, there's limitations :-/
I'd scrap it since Serenity doesn't visit the Sea Zone in canon, but it's there for Ignis characterization, or so Kim says.
Umbrageous Light's Sea Zone spans multiple maps, rather than just one map, but then, we're stuck with ~100 maps.
It'd be easier to remake LS in Game Maker (just not GM4), frankly.
Looking through Lunar Shadow's maps, I did feel that you could easily merge several of the maps (even if putting all the scripts together is tedious). Also regarding Sea Zone, Kim could just redesign the level and rewrite the scripts (which is what I did with Taboo Zone because it's original version in Gun v1 was reviled for it's dull level design and damage sponge enemies).