No, I mean logic parts don't count towards the total number of parts..
Logic parts are free.
As for the punch thrusters... How about having weight classes by thrusters then? Must have less than 20 thrusters, 40 thrusters etc.
Right now, there's no reason (that I can see) to have less than 100 parts. Once the logic is set (5 parts? 10 parts?) it's just adding more fuel tanks, thrusters and googly eyes.
Sumo arena is weighted more towards strength than finesse. So having the best logic bot (which is a huge challenge) is not rewarded as much as just more thrusters. Which is easy.
That's why I'd like logic parts to be free - so we can get some seriously smart robots, and lower weight classes so we can get thinky bots instead of strong bots.
http://robotwars.wikia.com/wiki/Weight_Classes