I think the best system to go would be a World of Warcraft typical style. 1234.
Due to the lag issues I've seen I believe this would be the easiest to go about changing into. I would much rather focus on other coding things than worried about lag and other issues that come with Mount and Dlade, LIF, and Darkfall/Mortal style combat systems.

Give us special attacks, and powers with faith. I'm not asking to jump around shooting fireballs. Just saying make some special skills and attacks.