This is what i got from OP' idea: instead of building a wonder, you build a wonder class, and the earlier you do it, the greater the bonuses; it also determines which thing, specifically, you built.
For example, say several nations are building a Great Tower:
The first to finish gets the babel tower or something
the second gets the great lighthouse
3. gets Porcelain tower
4. gets Leaning Tower
5. gets Eifel
6. Gets CN Tower
Then there's a Great statue; the first place gets the Colossus, second place gets Zeus, [...] eight place gets Liberty Statue, ninth place gets Cristo Redentor
Then Great Inner City (Forbidden City, Angkor Wat, Versailles, Kremlin, whatever)
Then Great Triangle (Pyramids, Ziggurat, Chichen Itza, Louvre).
This way you won't have duplicate wonders, and your production won't ever be wasted by losing a wonder race.
Personally i don't like this idea, first because it makes wonders progressively worst, which is the opposite of what we have now (early wonders have smaller bonuses but they are good, because your numbers are so low they make a difference; late wonders are very good but don't make that much of an impact); and second, because then everyone can have one of each class of wonder, which totally removes the uniqueness of having wonders in the first place. It also greatly reduces the amount of different unique type of bonuses we can get from them; we would then have a "growth" wonder class (pyramids); an economic wonder class (statues), etc.
The way we have it now, wonders are trully unique and the bonus they provide is more connected to their history and relevance than their actual usefulness: why do your workers work harder if you have a pyramid? Because it takes a very laborious civilization to build it; the colossus is just a statue, it doesn't leak gold or make ships appear out of thin air, but it is the symbol of a civilization that it well versed in the art of trading.
If we take the Wonder Classes idea, then Chichen Itza will just be Pyramids/3; ziggurat will be pyramids/2; etc. And then, the idea of each wonder giving you bonuses based on it's historical relevance will be totally lost. The civilization that (in real life) built the Colossus was totally different than the one who built the Statue of Liberty, or the Cristo Redentor, thats why they should have different bonuses.