How about the following:
Pull the dats today into the evaluation repository branch.
Have a test group of machines get their updates from the evaluation branch.
Have everyone else get their dats from the current branch.
When you are happy the dats in evaluation are good, move the dats to the current branch.
The update branch used by a machine is controlled by the agent policy so it's really easy to manipulate.
In your case you would perhaps pull today's dat into the evaluation branch and then move yesterdays dat from evaluation to current giving you the one day test period.
There is even a server task action available called "Change the branch of a package" specifically for the purpose of moving or copying packages around between repository branches.
You can use that to schedule the move of the dats around between branches as needed.
I must have missed that Server-Task I admit. Or I was looking in the Tasks for ePO 4.5 where there is no such a task. Thanks a lot for pointing this out to me. Now and with a feel of relief I can face the end of the Maya calendar