I propose that the DSP's default order be adjusted so that 'Tempo & Pitch' occurs before Headphone/Room Correction (and perhaps Convolution as well).
As it is currently ordered by default, any changes in playback speed will be applied after the audio has been adjusted to compensate for the distances etc. involved in the current speaker setup, which means that the end result will not sound like the source signal's speed was changed. Instead, it will, once again, sound improperly adjusted (because the carefully introduced per-channel delay value has been affected by the speed change). If the speed change occurs before these setup-specific adjustments are applied, then speed-changed playback will still be properly adjusted.
Specifically, this change consists of switching the 'Headphones' and the 'Tempo & Pitch' DSPs' default positions.
Please note that my reasoning is based on thinking alone (as opposed to e.g. an understanding of how stuff like phase correction works), and while I don't currently see how, I may be wrong.
Also, the change would, obviously, not affect existing Zones' current DSP order.