I’d be interested to see people get really creative with it. Throw a gym in on one floor. Cinema room on another. Storage units in a few more. Probably difficult to structurally support a pool on a floor not already designed for one but sure, let’s throw one in there too. A kids playroom is maybe a little depressing with no natural light but it could work. Hell: keep the middle commercial space and put a grocery store in.
Obviously once you’re talking about true high rises you’re going to run out of possibilities and I know the maths is still very rough. But it’s an interesting thought exercise to think about just how many amenities you could pack into a building.
Another use for interior rooms could be meeting/ conference rooms/ teleconference/ coworking spaces. Some premium apartment landlords currently have these in their clubhouses, usually reservable by the hour, residents usually get so many free credits a month.
Is this a thing, in planned conversions? If the pricing varied by day and time, or was dynamic, it could work very well. With secure lockers adjacent. (Would that require mixed-use zoning?)
A teleconference room (/remote classroom) by day could be time-multiplexed into a cinema room off-peak (with some compromise in seating plans), leasing company just needs to handle cleaning deposits and video surveillance at start and end to check users keep it clean.
20 Exchange in NYC is like that. Each chunk of floors gets a nearby amenities pod, with singletons for the really expensive stuff. Still, I think you’d have to get a screaming deal on the building in order to be able to make that economical.
Funnily this is kind of possible. Tokyo has at least one dance club located in a residential high-rise, just padded enough that the sound doesn't carry into the apartments around it. It's been a while though and I can't find the name now - please post a link if anyone remembers where it was.
Obviously once you’re talking about true high rises you’re going to run out of possibilities and I know the maths is still very rough. But it’s an interesting thought exercise to think about just how many amenities you could pack into a building.