Today the app allows to make A and B version and get results of it.
The best way to manage it would be to have the ability to send a A and B version to a sample of the database (like 10% of segment) and then automatically send only A or B to the rest of the audience depending on the sample result.
==> Choose the amount (%) of the sample
==> Choose your winner criteria (as today) and the date it should be acted
==> Send automatically the 100%-sample emails with the winner version