Collect multiple submission data sets in one form

Using a registration form we are trying to capture multiple datasets in one form. The problem we ran into is this.

For a car show vehicle registration form we had some people submit 2 and 3 cars. That’s fine and all but b/c they used the same email address and we’re syncing to MailChimp, we only see the last vehicle registered in the MailChimp database b/c MailChimp just updates the info on an email address that’s already registered in it’s database. We have to create separate audiences in order to log the same email address with a different vehicle. This is not ideal.

Is it possible to not allow a submitter to use the same email address or is it possible to give them the option to submit multiple vehicles in one form submission?

The single vehicle registration is already pretty lengthy and has it’s own logic system. When I try to duplicate it things get broken real fast.