Assuming density is mass divided by volume, we already kinda have density in the form of the weight property (since the volume of every particle is constant). Making the BHOL reaction take weight into account is entirely possible. As for how likely a change such as this is to happen in vanilla TPT... yeah, not likely. New reactions are seldom implemented and old ones are changed even less frequently, and practically never if the only advantage of a change would be that the reaction would mirror a reaction in real life more closely.