Hiya, welcome to the sport
The 'active weapon rule' on heavyweights isn't actually in force at the moment, I don't think it has been since Robot Wars ended. It certainly doesn't filter down to the antweights in any case as we run by
our own rules and passive robots are most definitely allowed, in fact having 50% of the arena as a dropoff zone encourages them to an extent.
As for competitions, there are tech checks of every robot before the 'big' competitions (World Series, etc.) and most of the small tournaments, to make sure they comply with the rules, and even without them you'd struggle not to get a lot of fellow roboteers giving your creation the once over and offering advice (and me with my camera), we're a personable enough bunch in general
A 6WD pusher might be an interesting technical challenge inside 150g and a 4 inch cube, but good luck with it ^^ most events tend to be towards the south end of this sceptred isle so you might be hard pressed to find something local, but I'm hosting the next Antweight World Series in Pontefract, in West Yorkshire, which is probably as local as you get, and you're more than welcome to make that event your first one.
Hope all that helps
