I am not sure there is actually a technical limit to the amount of Wonder Projectors, other than in-game default. Out of game through tools/mods, it is certainly possible to add more. The data comes from the building object’s data; Message field. It contains a base64 string, which is a conversion from hexadecimal to understand better. This data is indeed used through Discovery Services (local save/server). How much of it actually comes from the server I have not tested enough to know, but I am aware not everyone may see quite the same, at least when it comes to custom naming. Some have reported to me it looks as expected, but seeing procgen names instead.
As for the Message data that is included with the base building part, it can be converted to hexadecimal and will then contain the Universal Address (UA), Wonder Type, and various IDs required to make up the visual (species seed, creature type, etc) to represent it. This info can all be found in the Discovery Data of the save as well. Just be aware that these would be using little endian format (basically reversed byte order).
I could probably give further detail and examples, but that is the main gist of it.