I'm gonna be the first sad to see Corporations gone here (Publishing was my other, obvious, vote).
Not that they were that useful late-game the way they were, but I think they could have expanded on the concept.
- Guilds could be an earlier, more accessible form of Corporation.
- I liked having to go for the base tech (Corporation), then needing another tech down the tree AND a specific Great Person. Made the corps something far more fulfilling to pull off than religions.
- I also ADORED the emphasis on collecting multiple resources, planning out even land conquest for comboing many resources. Gave resources potential new purpose, but then what they did with Strategic resources partly makes up for taking corps out, and shows them to be in the right direction.
- It had an alternative way to use, if you were small and (literally) unresourceful, that you could not get the benefits of your own corp but instead get loads of cash from touting it to the seven winds. With gold having more use now, it would be an even nicer strategy.
- They didn't skew diplomacy like religion did.