Agree with Degs29. Allowing them on GL is a disaster. My top 10 in SA is all LV teams, no way past. In TW, the team with most LVs will win as you'll waste teams trying to take him down.
My suggestions would be:
1) To make them inactive if a GL is on the team.
2) Tweak the incoming sets so that each character bonus is a benefit against 1 or 2 teams only e.g. There's an (Omicron or Datacron ??) ability that gives immunity to instakill, that's obviously of benefit against a JMK/CAT or SEE/Nihilus team but not much help elsewhere. The previous JMK Datacron that ignored protection would have been great on normal toons to counter JMK or JML teams etc.