I have a RYTM + Octatrack combo and the Tempest. Everything has it strength, i play more with the Tempest because it sounds better to my ears. The RYTM is a bit stronger in the bass department, and the sequencer probability trigs is really cool.
What i think a welcome addition on a drum computer would be fades to control the volume.
Tempest 2 wishlist:
FX, (better saturation) delay, reverb, stutter fx.
Sample import via USB disk drive.
Midi probability triggers like on electron, polyphonic external sequencing. (The new faders would also work as velocity faders ?)
Internal resampling. Two/Four tracks to play the re sampled files.
More filter type´s, different flavours.
Especially cool if it would have insert FX not just send FX.
8 Voices + 2-4 sample track (with analogue filters.)
Faders for volume of each track.
Waldorf did something like digital osc, analog filter and then resampled it for digital FX, i believe that is a good idea.
Wavetable synth engine + morphing on one track would also be cool with user waveshapes.
Essentially the Interface from the Tempest, added with some faders for volume control + a small sample section on a extra screen for file access /browsing.