I completely agree! If Roland want to address the needs of younger players, and make arrangers more popular with the players that are buying synths, loopers and the like, adding some sort of audio looper that would run in parallel to the arranger or SMF section would go a VERY long way to doing this!
They already have a budget keyboard (the VR-09) that has an audio looper built-in. Simply port the code for this to the BK-9, job done!
On a related note, I'd also like to see the option to turn off the Chord Recognition, and have Patterns use ONLY the notes played. This is essentially what most arpeggiators do, and this is the core of the modern loop/arp sound. A combination of some tracks substituting the played notes for the recognized chord, and others playing ONLY the played noted would radically expand the sound of the arranger.
If this is complicated, then at least let us have a WS-based arpeggiator along with the standard auto-accompaniment. Best of BOTH worlds. Personally, I don't feel either system alone gets the job done on modern music. You need a combination of arranger, arpeggiator AND audio looping to have a complete instrument. Each of these features is available on an inexpensive Roland product, but no product combines all three yet. I bet the first keyboard out the gate that does all three will utterly clean up in the under-30 market! Roland, you have an opportunity to lead the field instead of playing catchup... Will you take it?