Mayhem gives us almost everything we could want for a modern/near future city but the one item it lacks in is the really nice well kept parts of town. Shellendrak makes a good start for a monor house but dosn't quite cover it all and it got me to thinking about...

The Penthouse- A skyscrapper highrise for the rich and weathly to live in, while the actual de3signers may be able to come up with some better ideas on how to do this I've given some of my ideas for how something like this could be done

What it would need:
2-3 Exterior textures, each would have three first floor walls (one with door and two varients without them). and two upper floor walls (variants of same textureing)
2 First floor loby tiles, these would be bet if made with one solid floor design and modular walls so you could add in offices and such behind the desk.
3-4 Upper floor tiles, these would have other flooring options like carpet or real wood but would still have modular walls to make individual rooms

That would give you the skeleton of the building but the thing that would make each one unique would be the interior options:

Dropins- Dropin tiles of two by two inch with some other floor designs plus maybe a couple of the ones from above, so that an individual appartment could a different look than rest of the floor (real wood for the rooms but carpet in the halls or vica verca)

Modular walls- Two for the lobby and two for the apartment areas these would be blank (as in no pictures, hangins or other decorations) so that only a 7" wall is needed, just cut to fit.

Wall Dressings- The pictures and such missing from the walls are then added to make each appartment unique

"Flats" floors- Simple outlines/templates to cut out and make a blank box fold so that you do not need to make every floor, just the ones that matter. If there is noone on the fourth floor (or all the rest) just make four simple bozxes to suport the next level and place inside. (another idea that just struck me would be to just have cornertabgs like you already use that support the walls for the next level. Either way would be so that the empty floor i just htat, not even any need for foam board to put under it (but if you do you could come back later and fill that floor in...)

Balcony- Every apartment wouldn't need one so a seperate blacony peice that could be added onto the outside (maybe use lower half of exterior walls and matching/similar floor tile). Another option would be to just trim the walls to make a cutout and have the exterior flooring for it so the balcony dosn't actually extend outside the building exterior walls.

Stairs & Elevators- The elevator's not working hero, its gonna be a long walk...

Props- Go hog wild, luxury tubs, beds, expensive furiture items, statues, busts, whatever someone with insanely more money than me might buy...

Other options- Two "roofs" one is peaked with some small area inside and the other is flat and has its own mini mansion on it (like in Spiderman movie, though I've never seen one in person) and a drivway/ramp area that extends outside the building (the only exterior ground tile needed I think) with a covered awning for valet parking.

The finial note: While the floor tiles and walls would still be the standard 7" (or 7.5") the set itself wouldn't be designed with a 7x7 footprint in mind. The individual compnents may be based on 7 inch but a completeed and non kitbashed building would be built for either a 7" x 14" or 14" by 14" foot print.