You definitely ain't wrong about the summon materia. I believe there was one that breaks that limitation, though you would have to go through the process of Chocobo breeding and racing in order to acquire it. and even then, the corner of the map it's on isn't even marked. (Honestly surprised you got Bahamut Zero though, I never pulled that one off on my first try)

It is one of the very few RPG games that I ever 100% completed, but looking back at it now, there were definitely things that could have been done better, as well as things that were left incomplete.
One cannot help but wonder what could have been.

The remake revisits aspects that were dropped early on, only to be reset by a force actively setting things to the original release... It feels more like a sequel in disguise.