The game would save gigs in memory if they just reworked the graphics engine. Any dat editor would know that this game runs it's 3d models and textures into the same dat file and that gear of the same type but different texure both have their own seperate dat file with their own seperate 3d model and rigging information. For example the nation aketons. I could go in and edit the way the bastok aketon looks without affecting the sandorian model dispite them both sharing the same shape. From a storage standpoint this is horribly inefficient and causes alot of duplicate data. It would be alot better to have a set of models rigged to the character skeletons saved seperately and then save all the textures on their own.
Someone explained it to me a long time ago though that the reason they don't change it is because of how the ps2 needs to run the game, how true that is I'm not sure of, but I'm sure there are alot of tweeks that could be done that could free up space if not anything else to let it continue to run on the ps2 with new content.