Outright changing a key is not possible with how the key database is set up. You're free to register a new key and use that, though it wouldn't have a membership. But for that you could try shooting the BYOND Staff a ticket via the support form to see if they'll swap over your membership.
It is VERY rare for memberships to be transferred over. There's only a few circumstances where it is done and "making a new key" isn't one of those circumstances.
Wouldn't it be more practical to set up a system where you could change hub authorship? Hubs are pretty much the main reason you'd get membership in the first place.
