What that even be? You can’t fit what’s in the pro line in a smaller phone. The smaller phones already had smaller batteries, would you be willing to give up more to squeeze in another lens? Something or some things have to give when you have less space to work with.
Apple made the best small phones anyone had ever made and people didn’t like them. Bigger phones allow for a lot more than just bigger screens. People seem to take all the non screen stuff for granted.