Well, that's also the problems I see with the Fx(whatever). I will not buy it, if there is no proper OS on it. And for me stock android is definitely not a proper OS. So for me it's like that:

Fx with only stock android -> I will not buy
Fx with Lineage or similiar OS -> I will maybe buy
Fx with Sailfish, Maemo leste, UBports or plasma mobile -> I will definitely buy!

....but only if most things work. A little bit buggy at the beginning is no problem for me. But I'm not willing to buy it just as a toy