Considering how players enter games with a choice of 3 garage slots, it does make player balancing complicated.
I'm also gonna sidestep the existing balancing posts that are more focused on other game mechanics (amp cost, block attributes).
I wish to target 2 groups of players specifically, aerial players and medics.
Aerial players, in particular tsticks and flyers, have huge game impact. IMHO, even with perfect game balance, in terms of amp cost, block weight/hp etc, a flying robot will beat a ground robot all the time.
(I'm not sure where to place blimps on this, I've yet to see a particularly effective one that can dominate the game)
Its incredibly annoying when the enemy team has 3 flyers, and your team has none. The match quickly becomes a one sided affair.
To a lesser extent, I feel the same way about medics. Having no medics or too many medics really hurts the team. I'm guessing the "use medics to earn more credits" meta is catching on.
I'm suggesting a maximum ratio of 1 aerial and 1 medic per 5 players.
So in a 5v5, only 1 aerial and 1 medic bot is allowed per side. Once someone has already spawned in as a flyer or medic, subsequent spawns are disallowed.
edit: since a fixed ratio is proving problematic, how about a tandem ratchet system?
You may only spawn an aerial/medic robot if the enemy team currently has the same or +1 number of aerial/medic as your side.
This will help prevent lopsided teams where its 3 flyers vs 5 ground robots, or self sabotaging team picks like a group of 4 medics on the same side.