Nice write up and good ideas I didn't even think about.
For the gameplay I do believe there needs to be a new system developed to avoid the problems you said but to also be better connected with the barista. What I mean by this is that her happiness is affected by you wasting her breast milk by either spilling or dumping the drink. I also thought of the ability to sneak in breast milk to drinks by either just adding it or replacing regular milk. Customers would know but would slowly draw more people asking for it.
I'm also glad someone else thought of clothing cosmetics. You even brought up different mechanics with said clothing and that would be neat too.
I have a post if you want to read through what I thought.
https://itch.io/t/2663255/my-002-suggestions