Yes! Agreed! Would love to have this capability to test best performance of lead capture. The only temporary idea I could come up with is cloning the landing page and creating separate pop-ups and depending on the method of deliery, take email for instance, send half the emails with one landing page link and the other email with the treatment pop-up.
Still trying to come up with ways to just split test pop-ups without any sort of method of delivery and maintain randomization of the audience.