I think it is a mistake to equate MF and 35mm too much. They are pretty different and how you use them will be different.
A few key points -
MF maxes out at 1/500 usually. That is pretty slow for some work. BUT it flash synchs at all speeds. Great for studio work.
MF handles VERY differently. This is not a "grab and go" camera.
What I would do is this -
Split the difference.
Sell off the F5 body and maybe a lens or two.
Buy an N80. Yes, buy a NEW or slightly USED N80. Why? Because it is cheap (last I checked around $400.00) and will take ALL your lenses and makes a GREAT backup for the D100. In fact they use the same body.
Take the rest of your cash and........
Don't buy a Hassy.
I know, this may sound odd, but the Hassy system is expensive and you may not like MF when all is said and done.
Take that cash and buy something else. Used.
I suggest the Bronica ETR system.
Bodies can be had cheaply, the lenses are VERY good, and are cheap. At KEH.com you can get a nice ETRs with a 75mm lens (this is a "normal" lens like a 50mm on 35mm), with a 120 back, a finder, and a Speedgrip for around $600.00. The nice thing about the Bronica system is that it is VERY compatible. Very few things to worry about compatibility-wise. I use one and it is VERY nice, VERY reliable, and VERY underrated.
I mean, you could easily get $1,000ish for a lens or two and an F5 body (depending on condition....) and get an MF starter AND a good film back-up body for the D100.