Out of the two, which one would help you more right now: a full random roster generator, or the ability to import and export roster data yourself?
I would say import/export would be much more versatile... not only for me but I'm guessing for anyone using the Teambuilder.
Say I wanted to recreate, for instance, the 1985 Chicago Bears. I could probably go find a roster somewhere online that's going to have some of their info, like positions, age, height, weight, college etc. and could put this into a spreadsheet/CSV, then upload it.
Then again, also if I was in the Teambuilder and selected a team type, it would help if it could generate a 53-man roster with unique randomized players and attributes.
On a side note regarding my franchise project, when I began my franchise and swapped out the 32 teams, that still left the free agent pool with real-life NFL players. Since I wanted an entirely fictional experience, I typically go into those player profiles and edit them to make them fictional, but it would be cool if we could generate a free agent pool.