The thing is, it wouldn't be meant only for mages. This Is why I suggested getting it in the tutorial.
Nay!
Characters with high agility/speed and the appropriate perk should have a similar "bullet time" ability. The idea being that your character, as an extremely fast/agile person can react with insane speed to situations.
Which leads me to "abilities." Abilities would be under the "Powers" tab (which also holds daily powers, magic spells, and enchantment spells). You select an ability just as you would select a spell. Abilities would be like the aforementioned bullet time spell, or perhaps a far leap (with high acrobatics) ability, etc.
Common things that all should be able to do, like shield bash, kick, grapple, etc, would be controlled by button combinations that we've discussed far too many times in these threads before, mainly using left bumper in context sensitive situations and combinations of that and left and right trigger (also being context sensitive based upon whether you have an open hand, two open hands, a shield and weapon, or double handed weapon, etc).