Ha, yeah its a bit of a mad one, there really isn't from my knowledge enough brewery's in one catchment area that they could walk to each of them. There will have to be some public transport used.
For that reason i was thinking Cork.
Blacks
9 White Deer
Mountain Man
Cotton Ball
Rising Sons
Fran Well
8 Degrees
Quite a lot in one county but there is large distances, eg greater than 20km