Commercial buildings are designed for higher loads than residential buildings: I think it is 150 psf vs 80 psf.

You could certainly force the bathroom placement with the wet walls. Code is code, and space folding does not exist. So if you only allow for 18” of drop on the pluming then all the drains have to be within fifteen foot radius of the sewer line. And the floor beams will limit that further.

That said, the responsible thing is not to convert the whole building but make a sandwich of retail ground floor, residential above, then commercial, then maybe real estate top floors. Weight carried low is fewer failure points for the building.

I agree with your other points, but does actually each unit need a dedicated AC?

I live in a building with district heating, we all get the same hot water. If I don't want to live in an oven during the winter, I'll turn down the heaters' thermostats, which lets less hot water in.

Couldn't we have a similar thing for cold air in the summer? Send the same temperature to everybody, and allow people to choose how much of that air they allow in their units. Shouldn't this also be more efficient than a dedicated AC unit per home?

Each unit doesn't need AC systems on the roof. Window ACs and wall units suffice. They are also more efficient than central AC due to the lack of ducts. And if the office was old (prewar) it likely didn't have AC in the first place so it had ventilation shafts and courtyards, and you could get away with not having AC in certain spaces that are far from windows.

Why is the surfside condo collapse specifically relevant for office-to-residential conversions? That building was built for residential from the start. And that building also had basically ignored a major maintenance issue for multiple years.

I’m sure that structural engineers will be heavily involved. While there are some things to consider or worry about, I don’t know that any of your concerns are actually valid things to be overly worried about.

They’re certainly all solvable and I have no doubt that the PE(s) putting their stamps on it will have valid proven solutions that check out mathematically.

I would rather it just be expensive to live in NYC

NYC restricts building height to restrict population by land area. There isn't really a need for small apartments since population density is the limiting factor not space. You could build a not much more expensive apartment building instead of a dorm for the same population.

I've seen some of this around ktown. The elevators are always tiny and dingy. Not a fan at all.

Among other things, a culture of shoppers who know to look upstairs

This already exists, especially in the outer boroughs. But of course I'd love to see more of it!

I have toured a few converted buildings in NYC. You end up with weird apartment layouts for reasons you mentioned. For example, a lot of the layouts were really long and narrow to satisfy the window requirement since office buildings are generally just giant square floors where you can have desks without direct window access. I think the other issues are running plumbing and electrical to each unit where an office building just needs a central room with plumbing for a common bathroom area.

Overall the economics seem to work in NYC since rents are so expensive, but I would imagine converting an office tower in a MCOL or LCOL city would be harder to make profitable.

It's very expensive. But $5 billion in tax incentives helps:

"the report warns that the city’s new 467-m tax break may be overly generous, potentially costing $5.1 billion in lost property tax revenue over 37 years".

Anecdotal evidence:

In the early 2000's when the dot com bubble burst, a well known commercial real estate developer here had the same idea because many of the large corporate buildings went empty or went into foreclosure or had various other financial issues.

He bought one and I was told by several contractors who worked for him that he would brag about the sweetheart deal the city gave him and how little he would have to pay to convert the buildings into town homes. Because of the dot com bust, he also got a bottom floor deal on the price of the building.

It took several years to convert, but that's kind of when the wheels started to fall off. 9 people (at last count) were charged with mortgage fraud in a kick back scheme. They tried to buy up a bunch of the condos and then planned to resell them at higher prices. They were using ghost buyers to get financing.

Ironically the developer was never charged, but several real estate agents and their brokers plead guilty to fraud. The developer had also bought several other buildings with the intention of doing the same. None of them ever came to fruition and by the time the 2008 housing crash rolled around, he had lost two of the other three buildings to foreclosure and I'm not sure what happened to the other one.

The developer just got lucky. Right time to buy low and sell high, but then once he was straddled with market cost of the building and no sweetheart deals on labor and tax breaks from the city? It quickly became apparent unless you have very, very deep pockets, a conversion like this is very expensive and takes a long time for you to see any return on your investment.

On the bright side if you google the name "Cloud 9 Sky Flats Hopkins MN" you'll see the building they used. There are several local real estate companies who still sell the flats and they are amazing with incredible views of the city.

Here's some articles about the Cloud 9 Flats fraud:

8th Guilty Plea Entered in $14M Cloud 9 Mortgage Fraud https://tcbmag.com/8th-guilty-plea-entered-in-14m-cloud-9-mo...

Developer Jerry Trooien unlikely to be charged in condo fraud case, attorneys say https://www.twincities.com/2013/02/12/developer-jerry-trooie...