May I suggess also that the tabs is probably not the best way to access each views, especially when there are a lot of them. Navigating through them is often a pain in the … Rhino is not the only software that offer that kind of interface, Excel, AutoCAD are in the same bag.
Probably more something like Adobe After Effects would be good. The idea would be a king of “group tab” (a tab with a dropdownlist within). So by default, Rhino could show only 2 “group tabs”, model views and layout views. In the model views tab the list could be “Top, Bottom, Left and Right” and the layout views tab could be empty as layout is not necessarily useful at startup.
I guess also that each group tab needs to be categorized. I see for now only 2 kinds which I already mentionned (group tab for models or layouts). So each group tab could be differentiated (icon for example) and maybe a plus sign (+) could be visible on each group tab.
There is my vision on this,