Is it not possible to shoot in HDV, upload to the computer in HDV, load the video in a DV project and scale it down, giving you 60P video?

It makes sense in my head. Haven't tried it, though.

it is possible - on Mac you could do it with JES-deinterlacer and in Windows you could use virtualdub and avisynth.

For the less impecunious there is After Effects.

did it work?

I haven't tried it on 1080/60i material yet, but I've been testing a method to convert 480/60i into 480/60p that looks promising to me. Going from 1080/60i to 720/60p should be quite doable (and probably darn close to ideal for the actual realized resolution of the FX1/Z1).