Nice analysis there. I think the biggest reason they fall flat is that wonder bonuses are just too simple. They're all "X hammers" with no rhyme or reason. At least the merchant trade route ones are more specialized - some are increased capacity, some are bonus to internal routes, some external routes, etc... I wish there was some way to "classify" the wonders, and then you could have a little more variety with the engineers. Like if one gave a larger bonus, but only to wonders built on water. Or maybe if there was an engineer that let you bypass certain terrain restrictions on a wonder, that would be awesome. Imagine having a great engineer that lets you build Venetian Arsenal without having to be next to an industrial zone? Maybe that's too strong a bonus, although if it didn't actually give you production to it but just let you start it, it would at least be an incredibly fun engineer to try to get.