A few comments from my side too - for what they are worth.
If 80mm is your thing and you don't plan to have other lenses, you're better off with a Rolleiflex. Hasselblad's strong points are interchangeable backs and (particularly) lenses.
Skipping the 80 can be a good idea, but not because of performance. Hasselblad lenses range from "very good" to "exceptional". So base your decision on the field of view, purpose (e.g. macro) and price of the lenses you intend to buy. Yes, you can replace a 80 by a 60, a 100, or (ideally) both. The 60mm and 100mm are very complementary and among the best (together with the 180mm) of the Hassy lineup. So to answer your question directly, in my opinion you will not miss anything by skipping the 80 and going directly to the 60 and/or 100. I have a 80mm which came as a kit with the body and which I now rarely use, my go-to kit consisting of 60/100/180. Be aware that all these lenses trade for higher prices than the 80, though.
About that 2/3 of a stop. It does not represent that much of a difference in practice. Depth of field (or lack thereof) is similar between 80mm at f/2.8 and, say, 100mm at f/3.5. About the extra light: If you shoot handheld you will typically load a sensitive enough film (e.g. 400 ISO) so you will not require the f/2.8. And if you use a tripod you will not use the full aperture anyway. I personally never had a problem with the wide-open performance of the 80mm. Obviously a tripod shot at f/5.6 or f/8 will be "sharper" - if that matters. A good picture is a good picture, even taken with the 80mm at f/2.8. No one will ever tell you "This picture would have been better if taken with a different lens." And if you were a pixel peeper you would post on a digital forum, not on APUG
As a side note, I realized that it never worked for me to compare 24x36 and 6x6 focal lengths. The format is just too different.
I also always say: whatever the lens you chose to start with, you will own them all eventually
Have fun, hope this helps, and thanks for reading my long post!