Hi Bernie,
somehow doubt they'll ever bother trying to give it realtime arranger functions, probably because it wouldn't be all that easy especially with audio tracks.
Still handy for backing tracks though. Only takes a couple of minutes or so to type in the chord progression. If song requires any additional editing I load it into Real Band.
I'm starting to play around with BIAB more & more.
Never played a country type song in my life, but after listening to some of the country real track styles decided to go thru my collection of song books & found an old nashville song book. BIAB style works really well with a number of the songs. Forgone my prejeduce of playing along to a midifile or mp3 if it actually sounds better than one of my keyboard styles. If my left hand is feeling sort of left out (haahaa) I play a pad. My PA3X ( psr1500 & ketron sd2 plus my softsynths ) are all midied via Band in a Box. PA3x is set to arranger mode, so playing pad with left hand, melody with right, is no problem. I can have different voices for left & right hand, i can even use the korg sts's ( sound setup's) for right hand with Band in a Box backing.

Haven't gotten into the RealTrack Jazz styles yet.

If you've got the real track styles, you really should give it a go. I've ended up muting 1 or 2 of the tracks for the songs i've tried. The pedal steel guitar tends to dominate and makes a style unuseable for certain songs. Leave the bass, drums, strumming guitars & it's amazing how many tunes the single style will work with. i even had a PA3X style playing in sync providing scat voices. ( freaky, complicated, but a bit of fun)

BIAB has a function that sends out it's chord data. Been there forever, initially for use with Roland RA arranger modules ( I beleive ) Used it years ago, but I'd forgotten all about it over the years. Decided to try it the other day to see if I could get it working with the Korg. Now got it setup with Korg & my psr.

anyway it's always fun getting something different up & running