[whpalmer4]

You don't have to use Mail as your primary mail app, it just needs to run with the account where you receive the email configured. It is actually advantageous to use a separate account to receive the tasks if you also read your mail elsewhere. Make yourself a separate gmail account, configure that account only in Mail, leave it running on the Mac, and you are set.

Omni says they are working on direct support for email if you use their sync server. That means you'll be able to use that approach at a future date no later than if they were not working on it, quite possibly earlier, but you won't know when until it is ready for external testing.