When utililized in the right way, touch screens can add very much to an arranger.. But it needs to be done very clever...

Take tyros 5 for example.. when playing live, you mostly use the two rows of buttons closests to the keyboard.. I think it would be wise to0 keep all those buttons in hardware...

But all the other buttons can be thrown into the touchscreen interface, as you dont really need them that much in a live situation.. style and sound selection can be done easilly from a touchscreen, because in a live situation, you have all your performances prepared in front with all your favourite instruments.

when creating a touchscreen interface you need to be sure that all push elements are large enough, if you ever played on the Wersi Sonic with its large 13"touchscreen you understand what i mean, the elements are so big, you cant miss them..

Other things to notice, sliders work quite well on a touchscreen, knobs dont.. thats why you need physical knobs more then physical sliders, however, you would preferably have both asignable knobs and sliders..

The oldfashiones sound interface where all sounds are cattegorised in banks also has had its longest time.. putting a few 1000's of sounds in just 16 banks of 10 instruments each quickly becomes unefficient

Its way better to cattegorise all sounds based on sound charasteristics. Thats how most software packages do it nowerdays, and if you dont choose your sounds in real time (because those are allready in yoru favourites and OTS banks) but mostly when preparing a new performance at home then this way of sound selection using a touchscreen and possibly an inputwheel works miracles

but you can use a touchscreen for much much more, like an X/Y pad, or just like a new kind of seuencer like for example the yamaha mobile sequencer on ipad..

however, keep in mind, touchscreens work better if they grow in size.. 12" (yes thats even bigger then an ipad) seems a good size right now..