Well, another suggestion:
Furniture, such as functional crafting tables, furnaces, beds…
I mean, crafting tables part would be useful in any utility vehicles (pickups, vans…) or RVs, furnaces for onboard «kitchens/heaters » (like in airplanes, boats, RVs…) and sweet beds for RVs, roof tents, or even first class airplane places?
Obviously all those will be usable. Maybe even add a way to define its efficiency in the json?

Added in V15.3.0.

Since you said crafting tables first, I'm going to limit this ticket to those only. Will be a good small step for such things, especially since I shouldn't need to code any extra systems for those parts besides the ones that open the GUI.

The bed could just be a different seat type that renders the player as lying down without changing the time or setting the spawn.

For sure not changing the spawn. Because all you'd need is a bed in the air setting your spawn above the ocean. However, changing time isn't a bad idea as if you have an RV or an airship you can sleep there. Same reason Archimedes is popular.