A quick question regarding:
feed several cameras to one Render Target
Before we start digging deeper into this → you want to see a view from single camera at a time, right? And cycle between the views.
Consider using a single camera and simply move it to a new location (you can use any scene component to mark a new locatin). Something along the lines of:
Much more resource friendly & easier to manage. There is a project sample attached to my post.
If you do have some additional requirements that would render this approach undesirable, do tell