The only way to improve performance, would be to rebuild the game entirely.
Every time you load a location, every single event that can happen in that location are all loaded at once. The one you see, is the only one not being hidden.
That's why there's been bugs of "multi-Jasons" or other characters appearing who shouldn't.
Graphics wise, there have been improvements over the course of the game, one lighting update in particular, also contained an engine update that removed support for some older Operating Systems. Model/texture quality updates would only increase the current issues with load times.