One of the things I'm finding is that I really wish I could import Unity assets directly (or more directly) into Godot. A lot of asset packs are set up for Unity specifically, and even if they come with FBX or OBJ, these raw files are often incomprehensible and unusable, just a bunch of textureless planes and boxes, since you're meant to use the set up prefabs. Importing materials would also be really helpful, as sometimes there are no clues about what texture goes to what model.
So I get that Unity super doesn't want you to do this, and I don't know if it would even be legal, but if it can be done, I would love it.
One of the work-arounds I've been exploring is Unity's FBX Exporter. It's still a pain in the butt to get Unity up and running and unpack assets. I don't know if you can borrow the code somehow, but it'd be great to do this in Godot, or at least a program that's not as big and lumbering as Unity.
Here are some examples of asset packs that work well in Unity but are nonsensical in FBX: https://www.cgtrader.com/3d-models/exterior/sci-fi/high-city https://www.cgtrader.com/3d-models/industrial/other/modular-tunnels (this one is especially annoying because all the textures are tga) https://www.cgtrader.com/3d-models/space/spaceship/spaceships-low-poly-3d-model-bundle-ready-to-game-collection (this one not as bad as the others)