Hmmm... while these do sound intriguing there are a few problems in what you're suggesting.
I'll start with Shapeshifting. There would be very few powers available and useful. Sure you could make the baddies think you're with them but what else could you do. We also already have "Shapeshifters" in the game in the form of Peacebringer and Warshade.
As for Mimicry, while it sounds interesting to see I personally would never use it. It sounds like a set that would be to hard to implement and could potentially cause lag issues while new powers were being set up for your use. And again the lack of possible powers. If anyone remembers playing Mortal Kombat 3 on the playstation you might remember a character who could shapeshift and mimic other's powers. It would be something along those lines where when you shapeshifted into anyone other then the person you were fighting there was a few seconds where you couldn't do anything while the game loaded the new powers. At which point you were getting your [censored] handed to you. Otherwise they look like very good ideas.
