We're a small, nonprofit library whose members pay a small annual membership fee. We use Koha for most traditional library functions, including as our membership database. Currently there's no way to check out to a patron if their account is expired, but sometimes, patrons tell us "the check is in the mail", etc. 
We'd like to be able to override the "Cannot check out! Attention
Expiration: Patron's card has expired." block on checking out to expired patrons. 

Currently, the only option is to renew them, check out, then roll them back--which introduces more user error.