They're calling it Time Warp.I can see this being something Blizzard would consider. It definitely has the "cool" factor they seem to be going for.
HOWEVER.
I think it would be cool (just me) to have the [Stop] have the player pick up exactly where he left off. In other words, if you Stop that priest in mid-cast of a heal, when the stop ends, his cast starts up right where it left off. I think that would give it an interesting give and take, like the fact that sheeps heal the target (or used to anyway).
I think Stop would make an awesome addition to an Arcane mage's arsenal, but it would have to be made a deep Arcane talent, because it would give Frost mages far too much control.
I'd also like to add that I think it would be cool if they gave their Bloodlust ability a similarly inspired name, like Warp Time or Speed Time. That way it makes sense, the mage is speeding up time to speed up party members'm haste.