Feature request: "Check Availability" button on Membership Request Web Part

Is it possible to have a little button next to the username in your Membership Request Web-Part called "Check Availability"? when clicked it will query the FBA store to see if it is taken before the new credentials are registered?

Like the way you can do when you register with Live ID, MSN / Hotmail etc. to see if your preferred email is available?

You can add it as a feature request in the issue tracker. Admittedly this will probably be pretty low on my priority list, as it does currently tell you if the username is already in use when you attempt to register.