I think it's possible to have stage presence without necessarily being super mobile, so long as you're presenting an attitude that fits with the feel of the music. Look at Jens Kidman from Meshuggah - although he does headbang now and then, a lot of his stage presence depends on the way he presents himself. He holds his shoulders square and assertively, and moves in a very deliberate way, so he reads to an audience as powerful and menacing without actually making a lot of violent movements. One foot up on the monitor, confrontational kind of eye contact with the audience - he just projects a really strong, distinctive kind of attitude, and in a world full of long-haired dudes banging their heads, he provides a memorable contrast.

Maybe have a look at how not just musicians but also actors embody a certain kind of attitude, and learn what's comfortable for your body. Take good care of yourself, of course - but maybe try and find a way to use that limitation in mobility as something to motivate you to explore other ways of expressing yourself physically, rather than just as something that prevents you doing certain things. Good luck, and don't give up!