Ok Lots of information to digest here but if im correct:
The Motors need to be faster.
I can add a second wedge/surface to the other side to give wider range of attack
4mm hardox sheet metal for the construction.
5s lipo for power.

My preferred budget for this is up to £80 each for the motors and £50 for the ESC's.

I already own a Quattro 4X6 Charger for Almost every type of rechargeable battery but my preferred option is lipo. I also do have a fire bag for charging lipos which I believe is required for events (and it should be).