There will be no classes. Other than the fact that classes affect focus range, it is a good idea, unless by class type you mean statistics of your character being similar to those of a class.
As I doubt you can focus or zoom in on something with your eyes only, perhaps there could be a spell or item that allows you to do so. Things like binoculars or telescopes/spyglasses were not invented within medieval times I believe (my knowledge is extremely meagre), we can have an item similar to that of the items I mentioned before.
This idea is pretty good as you can see things from a distance in detail, as well as get information of another army or creature and prepare against it/them before they or you get too close. By \'armies\' I am somehow thinking of massive guild wars, but I doubt that there are going to be many. Still, guild defense is good as explorer said before. Anyway, scanning a countryside as a scout or just admiring terrain, as well as other features, is going to make the game more interesting. Interesting idea...