Resending invoices, unless late fees have been added, may be problematic to begin with. You run the risk that the customer interprets it as a new invoice. (Granted, if they haven’t paid the first one, they may not be likely to pay the second, but the risk is there.) The customer statement seems like a better approach.
Your real request, though, either way, is for bulk emailing. The developer has mentioned adding that capability in the past. But so far, the feature has not appeared.