For my antweight i was planning on just adding some more armour that can be easily attached and removed and compete in the soz bots weight class with it as well. It would be a light soz, or a heavy ant. I could just a easily opt for 4 wheels instead of 2, or changing to a another weapon.

Its the same trick we did for tractor pulling, just add more motors to compete in more than one weightclass (super spetter was 5 V8 engines in the lightest setup, to 9 V8s in the heaviest).

Keeping it in the same weightclass should just as well be possible to swap, and have the heaviest setup weighed. I would insist however that it doesnt take up more time between fights to swap setups. The robot should be ready for the next round without delays.