Your description of the caveats of 16 tracks outweigh the benefits anyone has listed in any Wishlist request for additional channels. This is especially true in the latest versions of BIAB. Further as Matt addressed, older systems and CERTAIN low powered computers and CERTAIN RealTracks and the high-quality and fast settings in BIAB Preferences can result in overload conditions. In this instance Matt and I are talking about different issues of the same type. There will always be users with computer system that struggles with some aspect of BIAB, be it CPU, ram, RealTracks generations, VST's but my point was more general that users with computer systems that are older and weaker powered, PG Music has addressed these issues in the past and created options to turn off certain processes to lower CPU issues. PG Music has done a tremendous job and accomplished quite a feat in retaining all users to use RealTracks and RealDrums since their inception through this year's version.
What a disappointment it would be for PG Music to add 8 more channels to the BIAB Mixer and doing so deprive a large population of the BIAB community the ability to access this feature because their computer is too old or they have the wrong CPU on their system and no option to upgrade it. It doesn't matter and there's no benefit if 16 tracks isn't something all users can access and enjoy without it choking or crashing their system. I have no idea if adding additional tracks would cause any issues to older and weaker computer systems but this has been a popular request for years so I'm thinking there's likely some type of barrier.
Charlie I am a big advocator for opening up the 16 tracks that are available now. BUT I always have said that option should be a radio button option: That is the user could use those 16 tracks as they are now OR they could choose to have them opened up for whatever, i.e. MIDI, RTs, RDs, and/or loops. YMMV