I have made a mesh and got sleeper spawns working.
http://engifort.site.nfoservers.com/7dtdPrefabs/skyhigh.zip
Stripping loot might not be needed. Making it high risk; high reward might balance out. Its set to spawn lots of zombies more so than the vanilla skyscrapers. Some dogs and ferals should be a guarantee regardless of player level.
The feedback:
Exterior ****
Parking garage **
Interior ***
Layout **
Exterior: From the outside the front looks great but behind I noticed its windowless -_-. But because the front looks really good I give it a 4 star.
Parking garage: While I like the multi-layer underground parking, its environment is kind of ewww. The rebar concrete look wall to wall looks quite off. The bad aesthetics outweigh the good part of it so I give that a 2 star.
Interior:While I like shiny marble and dark granite, its overused. 90% of the building is just 2 texturs. Adding some carpet, redwood, drywall and even white granite to give it more color variants would do the trick. It being too grey I give it a 3 star. Also, so many doorways missing doors
Layout: The apartments are more like the studio type. Bedroom, living room and kitchen with no walls dividing them. There is only 2 apartment units per floor. From the outside it looks like it would have more than that. Overall It feels more like a commercial building than an apartment complex with 50% of the building being all business. I give this a 2 star
NOTE: This prefab has a low chance of spawning in because of its massive size. Those who add this to their game may have to increase length_multiplier in the street generator. However, drawback to doing this can also make larger gaps between small buildings throwing the urban vibe off