I can understand the concerns about effecting PvE use of the skills, but if you say, removed the gem requirement from just dispel and magnetic earth for the time frame I think that would be better than people spending millions on gems for a test siege. Neither of those skills sees any real use outside of WoE in the current game environment.
I'd also recommend a free repair NPC, because especially if there are no free glistening coats available, there will be a very large number of broken gears going around, which would quickly drive people away from the testing if there was no repairs available at the save points.
Edit@Morlord: I think that the iRO community has shown time and again that a large number of the players are unwilling to cooperate under the circumstances you described. Motivating a large group of players to gear up characters, ready extra supplies, show up on time and be organized is extremely difficult without some kind of incentive, and if the goal is an actual stress test, there needs to be something to help motivate the extra people.
Edited by Tolrin, 06 September 2012 - 05:07 PM.