As you presumably play a mage you are probably aware of this but while cleave damage on 2-3 targets (Arcane and Frost) or up to 5 (Fire) can be fairly powerful, Mage AOE on 6+ targets is not only quite weak but also terribly uninteresting.
Mages have three AOE spells but they are shared between all three specialisations, and two of them are virtually identical in damage output with the only differences being graphics and range requirement. Frost is capable of doing more damage than the other two specs (Frozen Orb is actually a very powerful AOE spell) but this requires the use of a 60 second cooldown and the cooldown is entirely passive damage.
I believe we can do better, and as you are all also stacking intellect you can probably come up with a couple of ideas of your own. I have no delusions of thinking that Blizzard will actually implement any of these suggestions (let alone read them, this isn't an official forum) but I thought trying to come up with solutions might be a fun exercise.
Personally I'm going to try and think of ways we could make these spells more interesting without resorting to adding new ones but if you want to propose new abilities then I am utterly incapable of stopping you. My ideas chiefly focus around adding additional effects to the procs we already use for single target, purely because I think this is more interesting than just sitting there channelling Blizzard.
So Frost is the easiest as it already has fairly competitive AOE damage (albeit tied to a cooldown). The most frustrating part about Frost AOE for me has always been that both Frozen Orb and Blizzard generate charges of Fingers of Frost which you then use for... pretty much nothing. There is no AOE option for FoF, because Ice Lance hits two targets at the very most.
A simple change for me would be to make every tick of Blizzard and Frozen Orb (if it hits more than 3 targets) grant you a stacking buff that causes Ice Lance to hit an additional target for 40% damage, stacking up to 5 times. Just like the glyph, but actually useful for AOE damage! In an ideal world, Ice Lance would also be castable while you are channeling Blizzard, in the same way that Monks can cast healing spells while channeling, but this might have PvP implications that I am unaware about.
Arcane is strange in that it seems to have the beginnings of an AOE rotation in place (spam AE for stacks, consume then with ABarr) but then Blizzard decided to give AM a flat 30% stack rate which is so pathetically small that you are unlikely to get more than two charges out of it before everything is dead.
Obviously this could just be fixed by giving it a 100% proc rate for Arcane Blast stacks above a certain number of targets, or if Blizzard did not want to do that then I thought about adding a buff granted when Arcane Barrage hits three or more targets at once which lasts some arbitrary length of time (say 30 seconds) and causes your Arcane Missiles to generate a small explosion at the feet of your primary target on every tick. This wouldn't have a chance to generate extra charges like regular Arcane Explosion, but it would allow you to continue something similar your single target rotation (or sub AB for AE) while dealing AOE damage.
In an ideal world Fire's AOE would be fixed by removing the target cap on Inferno Blast and returning us to the glory days of the Cataclysm, spreading Combustion onto 36 reanimated Icecrown whelps at a time.
For some reason I think this is not likely to happen.
Instead let's add an additional effect to everyone's second favourite fire spell; Pyroblast. If we once again remove the cast time and cooldown from Flamestrike (as a passive effect for Fire only) then I think it would be fun to allow it to proc Heating Up from crits, and for Pyroblasts procced in this fashion (by critting twice or Inferno Blast) to explode when they hit the primary target, dealing no extra damage to them but burning everything else somehow.
Personally I'd be happy if this just put the Pyroblast dot on everything but as I don't think that rolls damage and it has quite a long duration it would probably just have to do a single burst of direct damage. Either way, I think that'd be more fun than Fire's currently very limited options for damage when not cleaving.
So that's about it for my ideas, I could probably come up with some more if I allowed myself to add additional spells to the game but I wanted to keep things at least slightly realistic (whether I succeeded or not is up to you to decide). Anyone else got any?