Allow villages and other structures to spawn on floating island maps

In minecraft Java Edition 1.16.5 I played around with generating different biome variations of floating islands and noticed that most structures simply would not spawn. No Mansions would spawn in forest biomes, no village would spawn in any biome, no fortresses either. The only structures I could find were:

- "Mineshafts" (which are really just an assortment of wood and cobwebs under the islands which I think should be removed)

- "Pyramids" both Desert and Jungle Pyramids spawn, but they weren't complete. Well, I found one complete jungle pyramid in 1.16.5 which in 1.16.3 was incomplete.

- Witch Huts (although this only spawned in the air underneath islands)

Aside from the above, I found ships floating in the air (which was cool) and a chest near pools of lava with a pillar of some sort, but no other structure. Not even with cheat commands could I find a single village:

/locate village

Yielded no results.

I'd like to be able to generate floating island maps that allow all structure types to generate. My guess is that some of these won't spawn above certain elevations, and so don't. In such cases, maybe the spawn could be attached to a land feature instead - at least in regards to maps where the only land is above that coordinate.

Without all structures I could eventually make a village by curing zombie villages, but I would never be able to reach the end since no end portals generated meaning that I could never challenge myself with a floating island survival map.