So, I guess what you are saying is that UI3 would not be able to have this functionality unless something in the BI program was changed.
Right now the display of cameras is different using the browser than what is shown on the PC that BI is running on. On the web interface (above picture) there is 4 smaller camera rectangles across the top, the next row down has 3 (larger), the row after that has 3 (larger) as well. The PC has 3 rows of 3 each (all basically the same size), plus one on the bottom row (10 cams total).
From what I have understood from the previous posts, there is only one tab (Webcasting) that affects what the browser view will look like. Any other settings only affect what is seen on the PC screen. Is that correct?
If so, sometime in the future there possibly could be a "Browser Window Editor" where one could place and size the camera rectangles for what was desired to be seen via the browser? It seems possible. Nicer to do the arranging from the web side, but from the PC would be next best.
I'm new to BI having just installed it last week so I don't know the ins and outs and quirks yet...