You're forgetting that one of the main goals of brink is to be able to have even bad players coordinate with their team, let alone the people in a lvl16-20 pub match. The difference between high level pubs and comp games will still be noticeable, but it shouldn't be nearly the gap that it is in other games. So the weapons will already be balanced for high coordination.
Think mines would also be restricted to like 3 per team for 5v5 and 6 for 6v6.
As for Heavies, they are likely (little hard to say without having played the game) to be extremely powerful on defense and skilled teams would lock objectives down without a problem if they are allowed to have as many as they want to.
Yes, heavies are going to be good for defense, but I don't expect having 2 heavies on a 5 man team will be game breaking, its only barely more than 1/3 of the team.You need to leave teams enough room to have different strategies, or else the games will get boring. The moment you say there can only be one heavy in a 5 man team, you leave teams 3 choices. You can have 3 medium players and be a bit stronger, 3 lights and be faster, or 2 of each for balence. It would take a game revolving around constantly changing team dynamics and turn it into something with 3 choices.
