Well...this is really a variation of a theme. There are swingers who have friends they play with in the non-monogamous capacity and there are poly who don't love everyone they play with. You fit nicely into an open relationship arrangement.
My only warning would be your logical disection of something rooted in emotion. You may want only a FWB but you may end up loving them or visa versa.
What you are looking for is not absurd...not even unrealistic. There are people out there who suit the secondary model well. Married women typically suit it well. But there are lots of variations.
Sounds like you have thought through this and what you are looking for isn't unreasonable or out of the question.
...By its raw definition, without love it isn't polyamory, but it is definitely non-monogamy and there are a few of us here that can play by multiple sets of rules