However, one aspect which I believe is detering such development, even from the modding community, is that the wonderings are a 'first to the tech' type build. The fact that there is no race to completion eliminates the drive and impact of the wonders....or rather shifts the drive into research instead. The quality of the city in which the wonder is being built no longer matters.
I suppose that's true to an extent, though I've never really liked the idea of the wonder that anyone can build until someone has built it anyways. I've always much preferred the Age of Empires and Age of Mythology take on wonders, where it's a pretty building determined by the faction you're playing and can be produced by anyone who wants to put the resources into making it assuming that they have the correct culture to build the specific wonder, to the Civilizations take on wonders where they're globally unique structures that provide bonuses (some of which are quite significant) and don't even vary based on the culture which produced them. Beyond that, I don't really feel that the race to the wonders really adds anything interesting to the game; all it really does is encourage players to pick out the 'optimal' tech paths to gain access to the wonders and have at least one high-production city to rush it to completion (in E:FE:LH, you don't need the high-production city, but I don't really see that as a great improvement, and given the bonuses that the higher-difficulty computer factions receive, all that this really means is that the human player won't have any wonders unless taken by force when playing the higher difficulty levels). One thing that I do feel that Civilizations II did better than AoE/AoM is that wonders were irreplaceable if destroyed; after all, we have this structure which is supposedly so unique that only one of them can be built at a time, but isn't so unique that we can't build the same thing over again as soon as the previous one burns down (although it's also arguable that the replacements could be a lesser reproduction or a new structure designed to replace what was lost but not necessarily reproduce it and we just can't tell because there's a limit to how much detail you can put into a game).
I'd much rather see wonders turned into a way to make the various factions more different from one another than to see the game continue with the silly race to research or construct a specific building. If I want to build pyramids and I have the resources to do it, then it shouldn't matter that someone else already built pyramids; what should matter is if the culture of whatever faction I'm playing allows for pyramids or not, because it's cultural differences that determine whether or not something like that is built, not the question of whether or not someone else already built something similar.
Of course, it's also harder to come up with a set of unique and relatively balanced wonders which help to differentiate the various factions than it is to come up with a single set of wonders for everyone to use, which I rather suspect is a large part of why this isn't typically done. In E:FE:LH, I'd at the least want the wonders to be kingdom-specific or empire-specific, with the bonuses designed to help show the differences between the two alignments, but it's probably too late for that, outside of heavy modding.
As far as Ereog's Tower goes, I tend to agree with davrovana - it's a rather underwhelming structure, especially when you consider that the 1 per faction Forge of the Overlord towers give you a shard mana for a couple different shards as opposed to Ereog's single air mana, and Ereog's Tower doesn't have anything else worthwhile going for it (unless you're going for a henchman or sion build, as those are the only things that +1 fame per turn are useful for at the point when Ereog's Tower is likely to come into play, but there are easier ways to get that bonus). I also agree with perigrine23 that if Ereog's Tower were restricted to Conclaves, well, I'd much rather build the mana and research structures in my Conclaves before getting to Ereog's Tower.