I think subdomain user accounts are going to be an issue over the long term.
How do you foresee sub domains being a problem otherwise?
Please delete the account (and my apologies for the hassle).
If one can grab "admin", "webmaster", or one of several others, she can also get SSL certificates for the domain.
Would love a tip if anyone knows an easy way to fix this properly.
Yeah, seriously, spend $1/month and use Route 53 or somebody -- anybody -- else.