I have noticed that there are a few Civilization and player unique buildings that can be made.  I feel that they can get lost way to easily in the planet building screen.  I would love to see them get there own sub line on the top or bottom of the selection.  If it is a galaxy unique building, having your science advisory let you know it got build by you or someone else would be great. No forewarning as you can quick buy them if you have the cash.  Something to help make them stand out.  I would also think that some special buildings could be built on a tile that in not usable by anything else as they are  truly unique and they would go out of there way to make them.  just my 2 cents