I've always liked the array idea, but a 4x array whilst attractive from a light gathering and time on target point of view, seems like it would present several challenges: complexity, focus, system weight, simultaneous triggering, cost, etc...
I've settled on trying to build a 2x system using two Nikkor 600mm f/4 lenses (6.3kg per lens) as that allows for ease of full frame camera or other camera mounting and keeps the overall weight, ease of use and complexity reasonable. I just need to make or purchase some components (beyond a typical side by side mounting) to help mount the pair and get some time. If worse comes to worse it could make for some great binoculars, for someone with some very wide set eyes
Best
JA