In all honesty it does not even have to end there, imagine if you could custom tailor your whole combat experience, giving limitless combinations, and being able to design your party with real total cohesion.
Make archery shots customizable in the same matter adding elemental effects, knockdown, slowing, charming, splitting, bouncing....ect....ect.
Make items 100% customizable to high end crafters. For example, give items a value of 100 points. +1 STR cost 10 points, +2 costs 30 points....a full +5 costs 100. Wanna make the item grant fireball, or backstab skill, that costs a flat 50 . So you could make an item that is +2 STR, for 30 points, Grants backstab for 50, Gives 1 CON for 10, and +10 poison resist for 10 making a total of 100. How fun would that be?
The replay-ability of a game involving fully customizable spells, melee skills, archery, rogue ability's, and items would make for such an epic experience. The variety to combat would would be practically limitless.