innovative game concepts i've been toying with include the idea of some cool resources that require no era, and are in the territory of the cool powerful tribes land. then, have some of the other tribes require that resource in order to upgrade to a uber unit, but also have a weaker unit it upgrades to, like how a UU is set up. that way, if they are in bad relations to a cool tribe, they get regular units, but if they are on good, trading terms, they can upgrade to uber units. i'm pretty sure this can work.
eg: warrior --> swordsman --> foot knight
but, if they get an uber, no tech resource it goes
warrior --> hero --> paladin
it would be set up so as that the swordsman upgrades to hero, and hero to foot knight, and foot knight to paladin. swordsman and hero would be on the same tech, as would footknight and paladin. then, have the hero and paladin require a resource called Stone of Order or something, but the swordsman and footknight require no resource. the Stone of Order would be a no tech strat. resource.
it should work, and would add a nice element to the game
~Q