Just stumbled onto this mod not long ago (it's a fairly fleshed out FWB mod)

[Z0mBieP00Nani]

Thought I would draw some attention to it.

 

https://www.patreon.com/posts/no-strings-v1-40325465

 

I like the concept, I just wish it worked with WW. It says it does but it only means in the context of "it plays all nice like" with WW, there unfortuantely does not seem to be a hook into WW for sexual interaction (or default romance for that matter), which means the only way to raise or lower the "FWB level" is through interactions added by the mod, either social interactions or sexual interactions.