Thanks to everyone for the great replies.
I am contemplating what to do, and will take some time to think this over.
I have ZERO experience with DAW's or MIDI, and as jazzmammal points out, this lack of knowledge may make BIAB not worth trying. I didn't actually regard myself as computer-illiterate, as I have been using a PC for about 25 years, but since retiring 11 years ago I've done little with any software except for Microsoft Excel and Word, which I use daily.
Web surfing, spreadsheets, Word songsheets and online banking don't broaden one's horizons much.
That being said, I doubt anyone ever started out with DAW's or MIDI already knowing how to use them, so perhaps I could learn.

I know what WAV's and MP3's are. I'm sure this would be good, but it would remove my ability to do requests, which is a big part of what my audiences have come to expect.

I need no exact "cover" or tribute-type backgrounds, quite the opposite, just looking to make generic backgrounds.

Probably 55 of my annual gigs are "free", and about 7 are paid...so a large investment isn't practical when I might only have 5 years or so left for the "lugging-around-equipment" element of solo performing.

I'm leaning toward getting BIAB Pro, and a new computer [which I need anyway] and doing some experimenting. Perhaps I'll stay with a desktop, and get a laptop later on if I can become functional with BIAB. Thanks again everyone, I may shoot a PM off to those who indicated this would be acceptable. Cheers.