Arrangers have always been designed for the home player not the gigging musician, (That pros use them just shows how versatile they are) so the priorities are different.
Sorry to say, but if you expect to see items specifically for the pro player, then you will need to avoid the arranger, as you’re not really considered during development.
If you look at most OMB over the world, they use a keyboard workstation and/or organ with a separate computer or module for the backing, (Ketron seem to be the de facto standard for backing modules) not an all in one arranger.

Bill