One of the intentions was simply to provide with more Sauber C11 vehicles because Porsche 962 and Mazda 787B had a lot more drivers and skins. When running a race against AI drivers there was only 1 sauber for every 8 porsches. If you wanted a balanced number you had to manually select them to appear on track (and probably boot some porsches and mazdas). This task was not confortable and many people didn't even know they can do that.
Now we have 9 saubers, so that they appear in higher proportion automatically.
Also, 3 drivers were, historically, too small representation. There was other brave drivers who won races for Sauber team. For example, Mauro Baldi, who actually won 1990 championship sharing vehicle with J.L.Schlesser, and now "share" skin number 32 in the mod. Schumacher often shared car with Frentzen and Wendlinger, so they share 31 in the mod...
I think Sauber C11 was only 'silver arrow', but C9/C8/C7 skins could be interesting to watch.. or fantasy skins.. Can you imagine in black?