Primary email address logic

We have instances where client email addresses aren't being tagged as 'Primary', because the system doesn't enforce this and it's easy to forget. Problem is, only Primary email addresses show up in reports.

Could we have it that either:
a) the '…make this the primary email' field is mandatory, so the record can't be saved without an option being selected, or

b) have the system default the first-entered or only email address on a record to Primary?