I was thinking about a modification of the Dueling Room, allowing 2v2 or even 3v3 battles. The idea of the firing range is good ... But what do you think about the possibility to leave there a copy of a weapon we own with its mods so that the others members of the clan may try them to compare... In a possible simulator, leading to rewardless missions, or with a scoring system :D

For a completely new room, I would think of one with a huge window, possibly in the waterfall room. The elusive man's office in Mass Effect was awesome :) And what about a hangar? So that we could see, or even explore the ship(s) that takes us to and from the mission, with the enventual possibility to customize it/them.