Currently you don’t get anything for the XP you gain after level 30. That kind of screws with one of the primary reward mechanics of the game.
One thing that I would really like to see though would be if we could further refine weapons by playing a lot of matches with them, so here is an idea:
Once you hit level 30 you no longer gain XP for your character, but every time you accumulate another 20,000 or maybe 30,000 XP you get to pick one of the bar stats on one of your weapons and raise it by one.
You could keep doing this up to a limit, like maybe 400 or 450% distributed across the five bars. So that way you can refine your weapon, raise some of those bars beyond 80%, maybe offset a bad bar on an otherwise great weapon, and just really tinker with your equipment.
It’s a very small incremental increase, but it’s just a reward for sticking with the game and playing regularly. You get closer and closer to having your perfect weapons.
At least for me something like this does wonders for my long term motivation, because I like being able to work toward a tangible long term goal, rather than hoping to win a loot lottery to make any progress late in the game.