Hmm...customizable interface. you would need to rework the whole interface and make the things like health bar straight instead of round. Because it would look kinda silly to have this half round enemy health bar in the top left of your interface. ^^
But colours is a good idea. And maybe switch parts of the same design. So instead of the enemy health bar you have like a cool down bar for your main heavy attack.
I think this needs a little more workout before we can give this to the devs. But it's a good concept idea. :D