I think maybe having frostbite lead to freeze could work possibly????
Like ice beam could inflict frostbite, then have a chance to flat out freeze.
Or after thawing out, being inflicted with frostbite might be more akin to real life.
maybe moves can only freeze in hail or certain terrain/weather and inflict frostbite otherwise.
some moves could only inflict frostbite while others freeze (maybe only low powers moves inflict fb)
idk I really like frostbite but it seem weird to just get rid of freeze all together.