<< I guarantee folks would pay for that.. but i've never seen it (ps.. I don't want this job) >>

Neither do I but I enjoy using BIAB to make good covers. I always use midi to capture the groove of a cover and I only use free midi files. There's some truth to paid midi is usually more complex and likely to be more accurate to the original but in most cases for use in BIAB, none of that is necessary. In fact, I've never had a case that a paid midi was necessary.

I haven't found it necessary to use any external program, including RealBand, to get nearly note-perfect renditions of cover songs with or without riffs. Bob Calver is right, getting riffs are important, but BIAB has excellent midi capabilities and song construction tools. It was a midi based program years before it transitioned to audio. I'm sure RealBand can facilitate the process but it's never taken more than a few minutes to generate a good karaoke song in BIAB.

Here's an link to YouTube of a cover song I created with a distinctive riff done entirely in BIAB.

Listen to the music, Doobie Brothers cover using BIAB

BIAB Ultra Pak+ 2024:RB 2024, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.