Perhaps instead of each civilization getting two unique units and one unique building, maybe having each just get a total of three unique somethings would work out better. You wouldn't want many civs with three UU's and no UB's (too overpowered, especially units with consecutive life-spans) or three UB's and no UU's (too boring -- everyone likes beating face now and then, even pure builders), but having one or two would be a nice piece of variety.