The 120mm 5.6 S-Planar is my personal favorite Hasselblad lens - it is great for portraits, although it is extremely SHARP (some feel too much for conventional portraiture). I prefer it to the 150mm for a few reasons, mainly that I don't have to get a tube on it to get reasonably close. I use it for a lot more than just portraits, but it fills that niche comfortably.
The 150mm is a bigger difference from your 80mm though, which probably makes it a more useful kit unless you also want the 120mm for macro / still life, which is really what it is made for. I have 60/80/120/250, and I probably use the 60mm and the 120mm 75% of the time.
80 and 100 are very, very close in focal length, so you won't see a huge change there. I haven't used the 100, but I suspect for most applications the advantages it gives you will be academic (the 80mm is already great).
Honestly, the 80mm with a tube works well for portraiture as well. Or even without a tube! Many of the greatest portraits of all time where taken with a Rolleiflex with a similar 80mm Planar. Never under estimate the power of a good normal lens.