Just to chip in - have been a Rollei user since 1993, started with 6003, then 6008AF, and for the past 8 years with Hy6. I got it with a move to digital, and haven't really used it with the film back much. The digital integration with the Hy6 is really nice (first with Leaf AFI 7, now Credo 60), and its a great setup. The Hy6 seems to have less mirror slap, and you can pick up about 1 stop more for handheld.
A few things to compare with the 6008 - the Hy6 has the better viewfinder, electrical management, batteries are easier, smaller, and just the next step forward. Love the focus confirmation, which is a wonder to use, especially giving life to older manual lenses (I've had the 60 Curtagon for some 25 years... ). Also able to adjust focus offset, needed if using digital, probably less so for more forgiving film.
On the other hand, the handle is awkward for travel packing - the little screen on the handle is nice, but the outer corner is exposed if one is rough with the gear. I've taken mine into jungles and up mountains, so its not delicate, but it doesn't seem quite as robust as the 6000 series. In some way, I miss the 6003, with removable handle (for easy packing) and the slim film back. But wouldn't go back... Hope this is of some help. Just sent the mod 1 back to factory for service, and its all fresh and raring to go. Needed a couple of boards replaced.
Film backs are very rare and expensive, sometimes the factory suggests they are making more, maybe worth contacting them? The interior inserts are nice and small, but not as simple or direct as the 6000 series.