If we had a way to transmute stuff into silver/copper/tin you could make anything you needed via Equivalent Exchange once you got a philosopher's stone. Maybe start with one but nothing else on a flat map.
That would be the best thing ever.
After playing a while you should get a gigantic factory in the middle of a flat world. Bonus points if you could somehow make it build terrain, with the ores and everything.
Could be eventually possible with Redworld's frames. Frame + deployer + some means to semi-randomly determine block placement (keeping in mind formation of veins or deposits) = manual world-builder. You'd probably be required to have EE, though, just to get started, and to create further materials from light (collectors/condensers).
I went looking at a post Elloram made about the future of Redworld. There is some pretty serious potential in it, far more than I know I could ever grasp, being pretty unimaginative as I am. Really, the whole breadth of modding available in Minecraft, and the potential of it, may as well stop development on any further core features and focus on making modding easier (and perhaps allow mods to plug together easier) and more efficient processing/memory management. An exception might be villager AI; I don't know what the goal is there, though I'm to understand Millenaire and ToK already do a lot to improve it, but it's about the only part of core Minecraft that's still 'unrealized' by vanilla development.