I am unable to load MP4 video into iClone ("unknown CODEC" message).
I can load an AVI or WMV file, which means it could be used as a background and your characters could be animated to do stuff, sort of like standing in front of a large movie screen.
Is that what you were thinking of? What are you attempting to accomplish?
iClone 7... Character Creator... Substance Designer/Painter... Blender... Audacity...
Desktop (homebuilt) - Windows 10, Ryzen 9 3900x CPU, GTX 1080 GPU (8GB), 32GB RAM, Asus X570 Pro motherboard, 2TB SSD, terabytes of disk space, dual monitors.
Laptop - Windows 10, MSI GS63VR STEALTH-252, 16GB RAM, GTX 1060 (6GB), 256GB SSD and 1TB HDD