I think the retirement option for changing classes could work, but the sticking point for most people is probably the feeling that "it's not the same character" that comes out of it, which is true in a sense.
I, too, am hesitant to just bundle class changes in with the overhaul. Like Cov said, I see it as something rare and exceptional that a player actually wants to change the class of their character to align better with their concept. The rest of it I'm fine with.
If we're going to encourage the "retire and rewrite" method of changing classes, JNC is right - we should make note of that somewhere in the charter, or change the wording on retirement a bit to make it clearer.