I started working on the National Wonders a bit. Here's the first ones I have. Remember, this is scaled by map size, so you are looking at building 4 of the prerequisite building on a Standard map to unlock the NW. (That is scaled down from BTS. I remember 5 buildings being necessary to unlock National Wonders on Small maps.)
Amusement Park counts Hotels. I couldn't find anything better. City Park is parallel to Amusement Park and would add an extra tech prerequisite (Civil Engineering).
Computer Center counts Network Nodes, but this is with the caveat that Network Node is pushed back to Advanced Computers.
Courier System counts Stables. The concern I have here is that you may get locked out when Stables upgrade to Knight's Stables, but you can put off Stirrup until you need it for Chivalry. I thought there was a fix in place for this, but I am not sure if it works. An alternative would be to move the Courier System up to Monarchy + Horse Breeding and count Caravanserais instead.
Amusement Park counts Hotels. I couldn't find anything better. City Park is parallel to Amusement Park and would add an extra tech prerequisite (Civil Engineering).
Computer Center counts Network Nodes, but this is with the caveat that Network Node is pushed back to Advanced Computers.
Courier System counts Stables. The concern I have here is that you may get locked out when Stables upgrade to Knight's Stables, but you can put off Stirrup until you need it for Chivalry. I thought there was a fix in place for this, but I am not sure if it works. An alternative would be to move the Courier System up to Monarchy + Horse Breeding and count Caravanserais instead.