Mass Sprite Sheet Expansion Battle & NPC

Only real problem thst showed up with the vanilla math was the portrait offset table only has a 2 byte adress which only leaves room for about 82 or so portraits

That's right. I think the offset calculation based on ID * $320 is also a neat solution. In case of overflow you add 1 to the bank value. That would leaves you with 160+ possible entries, assuming you got 160 sprite (as far as the turtle portrait XD).

What I still find interesting is that the palettes for portraits are still 16 colors, but load 2 bytes at a time meaning 32byte color palettes for portraits (still 16colors though).

Yes, a SNES color is 15 bytes. The format is ?bbbbbgg gggrrrrr. It would pretty dumb from Square not to use 16 colors, based on the fact that every SNES sprites are 16 colors, even those that have a 8 colors palette (they're just not using the full potential).

Also don't get why it sometimes uses the direct address at C3/7000 and another time it sets the bank independantly, and adds the $1D00 to the value from the table.

This and also [absolute loading, such as LDA $C2/6F4D,X] vs [X value based on bank value independently loaded of inner bank starting offset] is done differently for the same stuff in the game code, such as font loading. I'm thinking it might has to do with flags already set or register values that are already there and in some case they realized they are saving two bytes of space by doing it the other way, but that's just a quick theory based on nothing really.