I hear what you are saying with the "FwB" stuff - I can imagine that if I were in your situation I would be looking for friends first, without the "benefits" - getting to know them well, seeing if there is the necessary chemistry there for more than just the friendship.
While it may be fine for others to want to make things sexual very quickly, I much prefer to wait and get other "ducks in a row" before I open up that subject.
Taking this approach for you also takes you out of "unicorn-hunting" territory - you have said that you want this to be a long-term closed relationship (polyfidelity would be what I describe that as) and those take time to build the trust necessary.
I like the clear, mature approach that you are taking and I wish you a lot of luck on your path.
"Listen, or your tongue will make you deaf." - Native American Proverb