The way I generally go about it is I create my overview map, then when I want to make a larger scale map, I bring my overview map into the document, scale it up so that the new area I want to map is the size I want, then I use that as a template guide for the new map. I simply trace the old lines on a new layer. That way, the landforms will be the right shape, and the towns will all be in the correct places, but I get the level of detail I desire. Once I have all of the information that I need replicated, I hide the old map and continue on with the new.
There are ways of getting a zoomable map like what you've described, but the processes I am aware of can be somewhat technically complex and far more cumbersome than the workflow I've suggested above.