1. Be able to DM the main game. 2. Move around the map at will. 3. Be able to take control of any baddie and play along. 4. To be able to add/remove any baddie, trap or loot. 5. Be able to place various NPC types.
I'm not really sure making quests live and/or changing dialog in conversation live really works out.
I know that other game is trying to make the DM a part of the game balance by costing them points to do this or that with a limited pool. Maybe cool, but perhaps not necessary. I guess I would look at it this way, we rather not have a pool and if you play with people you trust probably all good. Random groups... that is where we could see some lousy DM'ing without limits.