How about a button to turn spellcasting subtlety on & off? Don't buy enough and you're splattered under the feet of your raid. Buy too much and you lose that crucial ability to peel mobs off your squishier party members (as well as the slow-sit-root-and-scoot). A toggle button is the only reasonable fix. Seems to me that it's not exclusively a shaman benefit - I could see cases where rangers (do they get subtlety as an option?) or any kiting class could enjoy this.
I can't think of a single other AA where you lose class functionality, even situationally. I think that's by design, so I'd think if enough people like this, this should have a good chance of going in.