Could you maybe add an additional route to the Mario/Sophia section where you betray Sophia to Mario and then take him out somehow, claiming his villa and all the girls as your own?
Also, maybe when you're rich enough in the game you can buy up more of the building you live in and have the other girls living there? Give them an excuse to be available for any studio work or sex in general? I'd like to see an ultimate Harem Ending where your entire building is basically your porn studio with multiple wives/stars living with you.
A minor nitpick, but could the next route that requires frequent morning visits not be restricted to the same one day? Having Amelia, Phoenix and Charlotte all on Mondays only means that you have to sleep for a week before you can progress with any of them, and since the only recurring morning visit that I know of is River on Fridays that's three other morning we could be doing other stuff.