At the moment I am thinking about terrain. Roads are to be the first order of business but I am thinking about the big picture and what comes after, the buildings, vehicles and street furniture. Doing individual bits is no problem, integrating them together is a lot less fun.
Most of the stuff I do on tabletop is modern, near future or sci-fi. I work on the assumption that vehicles are going o play a part in any game I play. I like using models that are just about the right size rather than cardboard cutouts although this is not all that bad. I also like street furniture and just a lot of general clutter. The trouble is that foot paths and roads are only so wide and it's difficult to may this look good if all you figures are on one inches bases.
This in general reveals the cognitive dissonance of the gamer. I want something that looks pretty that I can game on easily. It's a bit like the old rule about building projects, you can have two of cheap, quick and well but not all three. Coming to think of it, if you work for my last employer even that was impossible. Maybe they could get cheap, if they got lucky, but that's another story.
A typical road/highway lane is anywhere from about 9 to 15 feet (2.7 to 4.6 metres) and yes I took time to work it out. So assuming that 1" on a tabletop is about 5" (not perfectly accurate but a good ready reckoner) that would make a road 2 to 3 squares wide which is pretty much what I am planning on. If you then put vehicles in, there should be no space between the vehicles. Parking spaces then become vast tracts of land that it can take an entire combat turn to cross. On a two inch pavement you can only fit two figures abreast in a space that should be ten feet wide. So you up the scale to make it more realistic. A typical human, with limited personal space issues could comfortable fit in a two be three or maybe three by three space.
One of my old bugbears is about weapons ranges. I like Conspiracy X, it is possibly my favourite RPG of all time. The combat system is nice and fairly well balanced. That has a drawback. The range for a sniper rifle, in the five foot scale would be (with my limited grasp of maths) about thirty three feet on tabletop. Hitting something with a shotgun becomes a challenge at around ten inches and more or less impossible at about twenty inches. Throwing a grenade more than about twenty feet is a challenge (in the real world). Better be sure you can throw it at least fifteen inches because (in Savage Worlds at least) the lethal circumference is four inches.
Setting up buildings often makes things even more interesting. 5mm foam core is about 1" wide in 1:1 scale. Not all that out for a modern house. If you put the walls on the edge of the building, you loose a lot of space in the building (you won't get away with it with 25mm bases and I use 2p bases mainly which are 25.9mm). I can see ways of getting around that but that makes for very complicated designs. At the moment, I am thinking that I put the wall in the middle of the square then I have a bit more wiggle room in the building and then I can use the extra space on the outside of the building for dressing up the building (bushes, plant pots, steps etc).
It makes no sense/it's not fair. So realism really has to go out of the window. So maybe you just make it look pretty.