I haven't really used mine much for portraits yet but I bought a 150 Mamiya 7II lens of Ebay for $600.
It may be a problem for very tight headshots since the minimum focusing distance is 6 feet, but for anything else it should be fine.
I'm not sure the dilemma you stated is just the lens. If you are planning on doing a lot of portraits with the Mamiya 7 II it could be a problem with loading film continually, unless you have more than one body.
With a Hasselblad system, or most "portrait" systems, you have the option of buying more than one filmback, which can rapidly be added and removed. I use between 4 and 6 Hasselblad film backs when I'm shooting portraits partly because I don't want to interrupt the flow, changing out film.
I think, although the Mamiya can handle 220 film, that it is getting harder to find.
This whole film thing could be another consideration in your decision making.