Hmm... Maybe toss in 10 or 15 marks on top of all the glimmer and rep the merc would get upon completing the Nightfall with his employer. As for the level cap, I think it would be fine to let anyone at level 30 and above sign up to be a merc. Doesn't seem quite right to bar players from signing up if they've already reached the proper level requirement for the Nightfall itself. Sure, a couple of level 30s vs level 30 Nightfall would be an even match (and even matches can be some of the easiest to lose), but there are plenty of people who have the skills to make up for their level; I've done the Nightfall as a 28/29 with my father as a 30/31, and we've consistently beaten it. The troll issue would definitely be a more complicating issue, but I would think your suggestion would work for a while. The problem is that people tend to find ways around rules like that, but that is something to be expected worked on. As for AFK issues, people who have not been active for 15 minutes can be reported and booted from the game by the employer; the team can then expect a replacement merc as soon as possible, much like how the Crucible works when too many team members ditch the game.