Gave it a whirl. Looks like it has potential but so far, I can't figure out how to apply geometry modes to a level's main display list lol. And you weren't kidding about the strain in Inside Castle, didn't expect to see everything rendered before my eyes hahaha.
But yeah, if I can figure out how to plant B6/B7 (182/183 lol decimal scrub) in a DL node that doesn't contain one (only checked CCM and Outside Castle), then that'd be fun to mess with the vertices. Looking kinda cool anyhow!
(I have no idea how to navigate the compressed ROM; if we were using an extended ROM, I would've just done it myself haha)
Update: I just figured out how this n64splitter works, pretty nifty actually. I can actually navigate the compressed ROM.
I see the editor does indeed edit the vertices as objects and finding the colour tag wasn't too hard, although is there a more efficient way of Unity to auto-detect the nearest vertex of the click? (Thinking back to the Banjo-Kazooie editor, which had a flawless vertex colouring mechanic)
In any case, as soon as extended ROMs are supported, this is a lot better than manually editing all the vertices. I just slapped on a black test after planting in the B6/B7 myself in the bin file