Yeah, it could, but it wouldn't be a very effective hunter since it can't move very agile-y. Likewise, assuming the physics are reasonable (not sure where they were left off in this regard), a very large veggy would spend a lot of energy if it wanted to turn to face an attacker to fire back. Though combined with aimshoot that might be a bit of a problem, since it wouldn't have to turn. But even still, I think it should be balanced-ish. Would be good to release a 'beta' version, and have people write bots for it, and see if it's in need of further balancing (ie: if veggies are overpowered). Maybe have shots disperse more the larger a bot gets, or something.
I want to avoid arbitrary rules that prevent you from doing two things (animal vs. veggy). It should be more that you can do two things, but you'll be less efficient than other bots that stick to one thing only. Like you can be a predator that makes chloroplasts, but you burn so much energy being an animal that you're not as able to quickly reproduce as a pure plant, and you're so big as a plant that you can't effectively maneuver like a leaner pure animal could.