You can setup Premiere to playback through another monitor (if your monitor has DVI etc. in) in the playback settings so maybe that would work. Also you could work in a 1080 sequence and then render out in 4K or whatever you might need.
The 720 signal formats are either 50fps or 60fps and at least the Blackmagic Ultrastudio 3D will not monitor if it’s a “non standard” 720-framerate combo.