It's a separate tool from Unreal Engine, so you don't need to constrain yourself to its conventions. You're also not going to use UObjects, its reflection layer, serialization, and all that other stuff for a tool that's strictly for version control. Plus you're going to tie yourself to all the issues and slowness of the engine. Epic made this mistake with the Epic Games Launcher, which is essentially an instance of the engine running, and a huge source of various issues.

As for Verse vs Rust, Verse is used in UEFN experiences, but it is _far_ from any kind of production state. It's also intrinsically tied to UEFN. It's not like you can download a standalone compiler or REPL for Verse.