Why not just focus on making high quality regional maps? This thing will never be a complete map of the world - besides crashing people's computers, very few people are going to take the time to edit the entire world at that level of detail. Remember, in theory these are modifiable basemaps. So this map will always be in pieces - and if you use a world map projection, many of those pieces will be highly distorted. Use a conic projection, or satellite photos, or something else that was designed for patches of the Earth's surface and not the whole thing. Then there can be several high-quality, modifiable maps of various regions of the Earth.