I know what you mean - g shapes on fret 4 with a capo give you Bb which is a pig to play on an acoustic guitar. basically using that example you want BIAB to play in Bb but show the chords in G.

why not use nashville notation for the chords? G would become 1 , C would be come IV and D would become V using roman numerals. I'm not sure of the way to set things up to show the chords in capo position but nashville is easy to learn and becomes almost second nature. G shapes and C shapes between them will give you any key you like with a capo. and if you are playing with a capo like me Bbdim7 for example or anything other than the basic cowboy chords is not something you'll ever need. that's why its called nashville -country music has been described as 'three chords and the truth'. mind you the three minors in G and C are useful too!