Interesting idea!

If theymos could be changed the profile username and put a word "Guest" under profile name by request, that could be a way to delete the account for private purposes or any reason that could be lead to negative circumstances to the users.  Or, ask to change your username and leave the forum might also another option.  But if theymos wouldn't be granted this request, there's no way to delete your account and follow the suggestions above.

I'm thinking a possible negative outcome of this idea above, might not good for the forum if there are too many deleted accounts in the future.