[Nonfractal]

So what are the rules here?

Modified chassis. Definately!

Motor speed limit?

Lightweight interior?

Let's all meet up at next winter's WHO rally sprint to find the winner?

And mine's a TR8, so that gives me an immediate advantage!

A suggestion is to keep it simple. 
The less rules the better.
The objective is to take this notoriously bad car, make it work, and make it look good. 
Possibility of a future proxy race or class and associated photo opportunity for slotracer?

How about this for a first stab? 

Scalectric or G .Turner tr7 body. No chopping the roof off (making it into a cabrio) 
58mm max width
Any chassis and side skirts from any material.
Any weight can be added internally to the car.
Any interior (but there must be an interior with a discernable driver with full head/helmet.
Four wheels are mandatory, all four with face detail or inserts.
No magnetraction magnets
No rare earth motors 
Car must have transparent windows 
Suspension is permitted 
Guide must not protrude beyond the front of the car when viewed from above.

Howz that?