Well, it depends on the keyboard they use. I've done some dvorak modifications on keyboards in the past, and if it has individual keys, could be done, if you're brave enough to open the phone up. But if they use that single plastic platter, from which all keys protrude, like many hardware keyboards use, this is gonna be hard.

The alternative of course is just an xmodmap remap without any stickers attached to memory, that's how one uses dvorak on a pc. For thumb typing this would be interesting, but maybe why not, a good "password" protection too, with the keys mixed up. I might even give it a go... :O)