If PhaseOne had a real working Lens falloff correction, I would also consider a phase back. Phase told me they are working on it but I will not buy based on promises again.
Capture One 5.1 - light falloff correction is there. Either the "light falloff" correction, the "vignetting" tool or LCC based falloff:
LCC shot:
[attachment=21017:lcc1.jpg]
color shift corrected:
[attachment=21018:lcc2.jpg]
color shift and light falloff corrected (100% correction here):
[attachment=21019:lcc3.jpg]
Of coruse, you could also use LCC based correction with the 645 camera, not just with the tech camera.
Sharpness falloff is also available.