Bit late to this and you probably got something good working now but I'm actually that guy who made Neon Utopia and yea I probably spent years trying to get a rocket jump mechanic as close to TF2 as possible (while also trying to keep the code simple) and it got to the point where I could even perform all the tech like speed shots or bounces
Sadly the project died due to Godot 4 having a new physics engine that broke surfing and some other things like the global illumination having terrible performance for me but worst of all even some newer versions of Godot 3.x were starting to break my project and I went from adding features near daily to basically never
So I had no choice but to quit but I may end up dumping the project on GitHub someday if you or anyone is curious how my code worked but feel free to add me on discord (imh_turtle) if you wanna talk about it some more and I can possibly even share and explain some of my code better there
Also hopefully I may end up reviving the project with all the knowledge I gained on how voxel rendering works without using meshes like Minecraft and now there's no need to worry about physics breaking or other things exploding on me cause it's all my own code and I even got this to where I now have my own mini engine for this and it's cool just how portable the code is since it's all shader magic so it'll work in any game engine