Just because they are on a cosmetically unpleasant regimen doesn't mean they are bad patients - they can't help what the previous doctor put them on.
I recently inherited a patient like this on 800 mcg Actiq TID for severe chronic pain. He was begging for something different because with those things you just yo-yo between being in agony and being semi-conscious. Converted him to fentanyl patches and he's a happy camper. I figured he was averaging 50 mcg/hr so I started him on a 50 and we subsequently bumped up to 75.
Converting from 1600 mcg 4-6 times/day I guess I would prescribe a fentanyl vest.
Perhaps start with a 100 mcg patch and work your way up. My guess is you'll end up somewhere around 150-200 mcg. I don't think you can overdose someone like this unless you really work at it.
Another route might be to start them on a scheduled regimen of methadone - about half what you think the conversion would be - and cut the Fentora dose in half. Titrate up the methadone and titrate down the Fentora until they are completely weaned over.
If they are candidates for IPM go ahead and see if you can get their med use down with that (or PT, CBT, chiro, acupuncture, whatever). If it's not something amenable to IPM then put in a pump or stim.
The above assumes you think the patient really has severe pain.