You have the quintessial starter pack.


Now to add wheels to the adapted batterydrills.

Then it's welding up a decent monocoque to fit everything in. Or bolting together a HDPE machine with the right methodes. Barrel nuts, Tnuts or M6 Ranglebox strip nuts.
With steel or aluminium angle, nuts and bolts as next, heavier option.

Don't forget to shock mounting everything.