I appreciate this may make some people roll their eyes, but I'd just miss love.
I'm not a traditional relationship for the sake of it person. I spent a long time single, and with my marriage, I didn't enter into the relationship because I wanted a relationship, or to settle down, or because it was the right thing, or because I wanted a shag, but because of love and a need to be with them.
We are married with children now, so all very traditional I guess, but it flowed from how I felt/feel, rather than looking for someone to fill that role.
I guess legally speaking we are tied together, but that's not out of fear or keeping us together, because we are eachother home, our safe place. I no more consider it a burden to be tied to him, as I do being connected to my own arm. The connection is natural for me, and I would sooner cut off my own arm, than split from him.
Fwb/RA/whatever clearly works for some people, and everyone is different. But I personally think you should just take like as it comes - if FWB happens, great, but if unexpectedly a powerful love comes along, and does sweep you off your feet, then taking that chance doesn't mean losing your freedom or clipping your wings, but can be really great.
I'm a bit of an old romantic though ;-)