It seems to me that a wonder victory is not so disimilar from a tech victory at the moment, since the relatively small amount of industry required to build them means that the build time is negligible compared to the time to research the required technology. This type of victory should be most viable to factions with a strong affinity for industry, rather than providing yet another path to victory for technological powers like the sophons. The construction of a wonder should be a truly massive INDUSTRIAL project on a system. Therefore I'd simply propose that Wonders be buildable from the start of the game, and so can be projects that you can continually work towards throughout the game. The amount of Industry required to build them would need to be very large, but it would provide a non-aggressive alternative route to victory for industry focused empires, at the moment the Sophons will beat any faction to a wonder victory, despite supposedly being 'poor builders'.