Long answer:
If you're able to pick the mech, regardless of whether you can pick the map, you are invalidating any semblance of tonnage limits.
If you're able to pick the map, regardless of whether you can pick the mech, you are going to "remove certain maps" that people hate...
Neither is an incentive for anything positive. It must come with a drawback to the "custom mode" or a bonus to the current system if this is in the cards.
Edited by Deathlike, 08 September 2013 - 11:03 AM.