1) Local healing brush, implemented in a similar way to Aperture (ideally) or failing that, Capture One.
2) Skin smoothing. Local version ideally implemented in a similar way to Aperture, global version implemented in the same way as the Portraiture plugin. Or just plugin architecture and use Portraiture directly, of course, but that's probably a lot more work :-)
3) Better highlight recovery, as others have said. Shadow fill works reasonably well in Phocus at least for modest amounts, but highlight recovery definitely lags behind other programs.
4) All adjustments available locally via masking, which I gather v 3.0 has made a start on (hooray!). Make it universal for every adjustment for which it makes any sort of sense.
5) If you are going the whole hog, support for other camera RAW file editing.
6) As others have said, purchase Aperture, combine the best features of Phocus and Aperture and release ;-)
Cheers, Hywel