Regarding world map, why can't it be like the region-detailed map you get when exporting legends (example)? With perhaps sites, etc. put on top.
Technical limitations...
The reason is the current map design (one of the things that is to be changed as part of the Myth & Magic non backwards compatible changes). The Mid Level Tiles (MLT) literally do not exist outside of the current world tile + the world tiles immediately adjacent to it (a 3*3 world tile area, and that area is shrunk further to a single world tile pre embark). When you enter a new world tile ones outside of that 3*3 area are removed from memory and the new required ones are generated from seed (and the remaining ones are shifted around), with some kind of logic handling modifications of the areas if they have been loaded earlier. Note that this is a simplified explanation: there are additional complications from the current map handling system.
One of the things the map rewrite intends to achieve is to decouple different levels of the world from each other, so caverns, etc. can be generated only as needed, which is particularly important in adventure mode, where you move along the surface a lot, but rarely have any need for the caverns (and into the rock layers even less). This decoupling ought to allow for the MLT level to be loaded at all times (but the detailed, in-game level still has to be generated/unloaded even if the surface is completely decoupled from the levels below [a maximum size world is 257 * 256 world tiles * 16 * 16 MLTs * 48 * 48 in-game tiles = 38,957,285,376 ~ 39 Gigatiles, each of which has to keep track of material, fluids, plant growth, construction, ... in it]).
Thus, it is a possible outcome of the map rewrite, which can be estimated to be released during the latter half of this decade, assuming the current plans aren't deviated from too heavily.