Been watching the demos of the ARX Brass board on the Roland site here (The NAMM video shows it the best)and as Dennis says any modern board out there can assign voices as shown in the Video, however most hardware arrangers do not have the processing power to do it at the same time as using all the other features, in addition there is always the possibility of running out of Polyphony as each layer (Oscillator) requires its own polyphony.

It�s a matter of suck it and see really

Bill