what about giving it reduced crit damage, but it also scales a little off base crit? so if you build crit you get some guaranteed extra damage but you can also high-roll a proper crit (the idea being the extra damage + crit would hit as hard as current gp with a crit)
AFAIK it functionally already does. Maybe it changed but I thought the base damage and sheen never crit. So you crit your AD and the base damage is unchanged. Pushed slightly toward haste and lethality.
Though as I wrote this I feel like I remember something about base damages critting. That should probably go away if it exists.