Buffing Mesmers?
More Shame/Guilt type skills in Domination, fix energy loss (which doesn't do anything in HM), lower recharge.
More AoE in Illusion to give slowdown/weakening/denial more effect against mobs, lower recharge, more skills that break the degen cap.
More synergy from Inspiration, skills that trigger every time you interrupt/hex/use a signet/steal energy/do all those mesmer things, thus providing a bonus for mesmerizing behavior through recharge reduction/energy gain/granting energy to the party/boosting attributes, and base them off of Fast Casting to boost primaries (kind of like Glowing Gaze, etc).
More Fast Casting uberskills. A skill that eliminates aftercast delay. A skill that decreases recharge times of your skills every time you interrupt. An elite skill that spreads all hexes from the target to all adjacent targets like Epidemic (and reduces duration by a percent that decreases with FC).
Give mesmers a reason to play their normal selves by rewarding good mesmer behavior, and give the primary profession a reason that it is better than anyone else at doing its own job.
S


(from a PvE point of view)