I agree with tchos.
I have some started project somewhere like this,even bigger in fact of some labyrinth city with hight bridge linking each part of street so you can go from one side of street to another using interior tileset ect.It change a lot nwn 2 feeling when size seem real..and if you miss door cause of building size you can always ad door with stair to lvl 2 house ect.
The main idea was if you can t see far away,you can play a lot more with the LOD to keep all detail around and put a lot of those little placeable that make a city lively.You could even make them 1 tri at lod 2 or even LOD 1 as they won t be in looking range.(as far as i remember,using fog to determine,lod 1 is around 80 and lod 2 150.Need to recheck btw.)
Making some reworked skyring is necessary too(and easy).The basic city one are ugly.I would open a simple one(like hill),make it a square keeping the side x/y;use a screen shot from some placeables houses as a texture for that square and just cut along wall and roof.
The possibility to ad simple collision mesh for a group of sided house is nice too (like the invisible placeable from sgk).I dislike when you can follow or shoot people not hided by building.But you need to have placeable entrance that extrude from the wall and it was easier as i created thing directly for my map and not really for other builder.