Most of the time I have seen fiber set up as a dedicate bridge device GPON to ethernet, the Optical Network Terminator(ONT). And honestly, I am fine with this. copper ethernet is much easer to deal. This makes a nice clear demarcation point, the copper past the ONT is yours, everything upstream of that is theirs.

Having said that It would be nice to have control over the ONT as well. there are PON sfp optics, that may be the easiest way to set up your own fiber capable router. I have heard it is tricky to to talk the isp into allowing your modules, you probably need to know a guy that works there.