The problem you will run into is that LPP renderers don't have access to the material's f0/specular color during the lighting phase. Quality PBR generally requires this information be available in order to perform per-light fresnel calculations. Now you could go the cheap route by treating the f0 like a color tint and then multiplying it with the final accumulated specular lighting, but it won't look as good.
That's my two cents.
EDIT: As an example, Satellite Reign used such a system, and only had true fresnel on their ambient specular.