If I understood this correctly, then, yes, a port of Nougat for the FP2 would be technically* possible.
But the FP2 doesn’t pass the CTS for Nougat. This is what I meant.
* Probably. But:
I would not consider buying a new phone which uses a chipset that is no longer supported in AOSP. And that was what I was trying to say.
If I had bought a FP2 when it first came out, that wouldn’t have been a problem.