Adjacency bonuses for Wonders

I would help get them into town and not in a war away no-man's land to max FIMSI out and get some line of sight.

Not exactly on adjacency bonuses, but related to benefits of wonders: maybe I don't have enough game experience yet, but I found many of the (at least early-ish) game wonders having fairly bland/similar and not that powerful bonuses for their investment. I was thinking whether wonders could also be differentiated by giving some more game bonuses, like adjecencies and in particular more interesting unusual effects, but making others primarily fame generators. Imagine a wonder that's worth 300 or even 500 fame. That would seem like another difficult choice between investing in the engine or harvesting victory points.