I like the quick swap idea. I think there also just needs to be more gear, both random and unique, targeted at hybrids. They could even have, say, both a strength and and an intelligence requirement. Also could be skills and talents that reward doing various things, like casting a spell increases your next weapon attack damage by 25%, as a simple concept.
I agree combined skills from two trees should either require or perhaps benefit from investing in both trees. Say, explode combined with battering ram makes you deal fire damage and light people when you charge: knockdown and physical damage controlled by man-at-arms and strength, fire damage and burn chance controlled by pyro tree and intelligence. Or there's an AP penalty for not having enough points in either tree.
