Today a variant consists of a map, a set of starting positions and possibly some rule changes. This could be decoupled I think, just like press mode is separated from variant. Think of chaotic, no neutrals and layered as map tweaks. Fog of war, build anywhere and octopus as rule changes. Standard, modern, empire, WWIV, colonial, etc are maps. Combining these alone would yield an almost infinite amount of combinations of exciting variants to play. I for one would love to play a chaotic, fog of war, broadcast only game on the WWIV map ;)
Perhaps such a restructuring would also make it easier to develop new variants? Sorry I meant easier to develop new maps, rule changes and map tweaks ;)