I think what would be cool is if you had more choice with grenades in all classes such as EMP's, Molotov's or even a grenade like a concussion grenade that slows players down. As well as this players should not only place turrets as an engineer class you should be able to place radars that would show all the enemy's on a map within a small distance.
When it comes to max leveling i think you should be able to continue to level 25 so you can get more of the high level perks and then when you get their you should be able to prestige therefore getting new skins for guns or new equipment or weapons but you would go back to level one again and loose all your abilities like in Call of Duty.
Anyway post what you think would love to hear from the Brink community.
Stay strong everyone.