I use a software called Mixemergency to video dj. It’s basically a Serato plug in and is quite the most preferred solution for many djs.
I’m not sure what the demand is for a fully functional controller that can show videos on the dual screens.
Something like the Pioneer RZX but not locked to any particular software like Pioneer.
Imagine a Denon MCX8000 Prime with the many suggested fixes and the added bonus of doing videos with Mixemergency, Virtual DJ, Mixvibes and standalone too.
For really good preview functionality, I think you’d need the controller to have three screens on it… left deck preview, right deck preview and outputs video screen, so you’d be able to see what the audience was seeing.
I doubt a lappy would be able to drive what would effectively be its own built in monitor/lid display and then two or three screens on a controller (as well as a sound card, a midi controller, and of course any DJ software.
But then again… for years and years, people have been saying that only a computer could generate beat grids… and look at what the SC5000 Prime can do…