The fact that the Celtic culture (and maybe the Germanic one, but I'm less confident on that) was a very advanced one precisely makes this MOD interesting,
Meh. If you want a modern-day comparison for the Germanic tribes look at some of Africa's more backwards nations imo. Ambitious warlords galore, strong and varied cultural identity, areas of peace and areas of anarchy, poverty marked here and there by a wealthy elite..

Chances are I'm wrong, but that's the impression I have.