[there should be a healing item for low universe runs]
“Miracle” heals (if I recall) five HP in the universe of your choosing, which IMO is generally more useful the fewer universes you have. It occurs to me that I could have the shop be more likely to stock items that it thinks are more useful to your current run, which might be necessary given how “bloated” the item selection has become.
The thing about those single universe target items is they take up a whole deck slot. I feel like there a sweetspot that is “Once per floor, pay 4 energy for 20 healing divided evenly across all universes you have, rounded down.” So if you have a four universe run, it’s super nifty, but a waste of a card in many universe situations.
Agree with your logic on wave collapse. It helps with the fun.
And also agreed on adjusting the shop inventory to match your current situation!