Ok, I think the CAD model is finally finished! The only thing I'm not sure about is the placement of the removable link access hole on the top plate, looks very axe-able, but im not sure where else to put it tbh.

According to Inventor, it current weights 11.5kg, with only the wiring/small electronics, fuse box, belt and a bunch of shock-absorbing things missing. So I should end up comfortably under the weight limit providing nothing is too inaccurate. If this is the case then I'll probably add some fat cuts of HDPE to the sides as extra armour.
It's basically threaded bars on wheels: