As you said, it's a lot of work.
Every single unit, building, weapon and item would need to be changed graphically.
On top of that, if this is supposed to be a polished graphical mod, you'll want to adjust all animations to suit the melee, weapon and item timings - which means even more work.
I know Touhou branches out in various directions and has its own fanatics, but for this project to take any foot, you'd need to combine an existing Savage player's love for Savage together with his/her love for Touhou together with his/her advanced skill of modelling, animating and modding. Realistically speaking, it's neither probable nor plausible; though it is possible.
How are you going to make your dream come true? Any concrete plans?