Looks like I was being conservative with my estimate of hundreds! I do know 3dsmax has consistency issues with icons because there are so many it gets difficult to tell them apart, not only that they are added at different times, updated by different artists. Its why the quad menu still uses a plain text format not icons, its why the UI is still very heavily text based because icons can work against themselves if their purpose isnt immediately clear from inspection.
Just to reiterate on a point I made earlier is that if an icon needs accompanying text then it probably doesnt do its job well enough, I will accept there is some middle ground where theres a need for both but if we consider screen realestate to be most valuable then perhaps you can get away with less icons or abit more reuse. One example of where its not very beneficial to touch on the icons would be the Content browser assets, we used to have just text and those icons are reasonably decent. If theres some way to blend the 3d and 2d icons it would be beneficial this way you dont have to make a set of thousands 
I do like what you did with the File menu in your latest concept, I thought that was a good compromise between the more modern large icon styled file menu and the old style menu bar. It makes sense to merge them so Im glad youre considering all options.
I was actually looking at the launcher too and I noticed its tabs are similar to what youre suggesting here 