I would like to see the return of the 'swing' knob, so you can change the swing feel of a style (from straight to slightly swung to stronger swing etc.) as easily as you used to be able to do on the old 80's drum machines, and a 'half time' button that would keep the hi-hats and percussion parts the same, but halve the time on kick and snare. Both of these features appear on Steinberg's Groove Agent soft-drum machine, and I find them incredible useful, and musical. I also like Groove Agent's MUCH greater choice of rhythms and fills (something like 15 or 20 variations and fills from stupid simple to stupid busy!). An arranger with the ability to have as many variations as you want would be MUCH better than the current limited choice.

I would also like the option to only have the drums play a 'pickup' fill if I hit Fill in the middle of a Break/Mute, just like a real drummer does. Most arrangers, if you hit Break/Mute for a mid-song break, you either have to wait until the end of the bar to start again, or if you hit Fill on the 'three' or 'four', ALL the Acc parts start up rather than just the drummer. Very unmusical!

Lock tempo to stereo beat-sliced loops is only going to be REALLY practical if all the arranger manufacturers adopt USB 2.0 for data loading - as it stands, the load times are impractical for live use. But when it happens, it'll be GREAT!