Sure you can change any building in to a storehouse where peasants will drop off their resources, but then the md file of that corresponding building needs to be modified and that is a mod and cannot be included with a map. Same as you, im not too much bothered if they just walk back into the mine, as long as they give the resources to the player.
I had a look at how gsc made their maps and some have a storehouse nearby though others dont, so i have no idea how to pull that one off.
Regards
E.A
EDIT: actually just thinking of something, there is one building ,under the test section in either neutral or dragon, cant remember now, which may have a resource base set up already, you can also create a mule there if i remember well.
I should have a proper look to see if that is the fact and if it can be used for this and on the gsc maps if they used this building.
EDIT2: nah dont bother, peasants dont seem to drop resources there, the only thing you can do with that building is create a packhorse
