ALL of the minor races have their own special, unique buildings - thats the real point of them in the game.
...Unless you're referring to the generic defense buildings. Any minor race that doesn't have any generic defense buildings is set this way for a particular reason; either they don't need them (Eg. the Edo don't need any because the Edo Guardian is all the defense they need), they don't want them (Eg. the Mizarians are
absolute pacifists), or their society hasn't advanced to the point where the concept of alien civilizations - let alone a war with such races - has necessitated the creation of defense structures against such occurrences (Eg. the Mintakans).
No one has ever asked whether the minor race special buildings should have requirements before; it was that way in BOTF, and I think most people expect it to remain that way. I accept that it is an unrealistic system though. There are certainly no programming barriers in implementing such requirements either - the minor race special buildings are trreated as any other. The only reason why these buildings don't have tech requirements is simply that none have been set.
Races that have multiple special buildings are those races that we have identified as being unique or important enough to need multiple special buildings. There is nothing as such that prevents all of the minor races having multiple special buildings. Or you could even have a system where players are forced to choose between a number of buildings - chosing one would obsolete the others and prevent you building them. Unfortunately there is a bug in the editor that prevents you from doing precisely this at the moment; the obsoletion system only works for structures that have *already* been built. If a structure has been obsoleted, it doesn't also get removed from the build list.
There are player experience issues behind adding multiple structures for each minor race as well. Each structure in the game requires a database entry. This entry contains all of the information about the structure - build costs, maintenance costs, tech requirements, a description, prerequisites, obsoletion lists, upgrade lists, and so on. This is a lot of information to process, and the more information that is added to the game the slower it will perform. The same thing happens with upgrades for buildings - the database considers upgrades as a separate building, so an upgrade requires a separate set of data, further adding to the size of the database. Adding one building won't necessarily result in a slowdown that the player will notice, but if you're thinking about upgrades for every special building, you're talking about 150+ upgrades, and adding all of those certainly could result in slowdowns.
Dafedz has created a database of all of the information relating to the game. You might find the minor race pages particularly useful because they contain information on all of their special structures.
Have A LookOh, and just for reference, the Gorn already have two structures, the Gorn Trade Alliance and the Gorn Replicator Net, whilst the Vulcans also have two structures, the Vulcan Science Academy and the Vulcan propulsion Laboratory. They have two structures each because they are both known to be large galactic powers.
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