For professionals yes, however, arrangers are for the home market, and if that was included as standard then they would alienate 99.9% of the arranger user base.
If it was an addition that could be added to an arranger (Much like Yamaha do with their iPad Apps) then it would be good, but again, only professionals would be interested, and would know how to set it up using 3rd party software anyway.
Remember, arrangers are designed to be simple to use, (Yamaha forgot this with the T5 and sales have been dismal compared to previous generations) and with the market declining, (At least in TOTL) manufactures do not want to put even more people off.
While it would be nice to have home and professional in one box, in most cases I would say it would put more users off, then turn them on. (Nice to dream though)
Bill