Why is master of many styles a 16th level feat. it takes my monk 16 levels to switch styles as a free action? it should be available as soon as a character is able to use two styles. Wouldn't that be first think you would want learn after you could learn two styles, is how to switch between them?
One thing I feel is that "more efficient use of actions" is a fine thing for a lower level power (e.g. Sudden Charge) but higher level feats should probably be a bit flashier.
Just because "I can save an action occasionally" doesn't exactly make you feel like a mighty hero.
What if were, switch styles as a free action at the end of your turn, and you can use this action to ignore the "open" quality of stances. Then you could go into a defensive stance at the end of your turn and use an action to go into an offensive one at the start of your turn.