[silvarilon]

I guess the "ideal" ratios would depend on your game.

Since ICO is set almost entirely in a city, there are few to no wilderness areas. We just have one or two rooms to represent "outside the city" where we take the PCs if a plot calls for it.

Other games may have a city and surrounding areas. Those wilderness areas could have a smaller ratio. (Are "lot of different nearby terrain types" really any more problematic than "I walked all the way across the desert in a few minutes"?)

Games that have multiple cities, especially cities in different countries, will need much larger wilderness areas to represent the space between them.

You'll also need to consider the activities that happen in the wilderness areas. If all you do is walk through them to get to a new area, then they can have a large ratio. If you'd be doing fighting, hunting, searching, etc. then you will want a finer grained ratio.

We have some plans for "distant places" but I don't intend to build the wilderness in between. Instead, there will be methods for travelling, such as hiring a coach. The PC would then sit in the coach for a short while, and then either "something will happen" along the road (for example, a bandit attack) or they will reach their destination. Leave the coach, and be in the new location.