Thanks for the feedback, and glad you're enjoying it so far.
1. No really worth the hassle in terms of complexity and the potential to throw off balance. In general it's much easier to "clean slate" each game. That's why what I did choose to carry over is story-related, rather than gameplay.
2. Again, once you start modifying stats with accessories that's a whole 'nother level of complexity to try to balance and play test. It also means an impractical level of sprite work, since I don't "layer" my sprites like some games. This means I have to do a new sheet for every combination if I'm going to represent it visually, which is obviously untenable. A few costume changes are doable, especially if only one shows up in fights, but not so much for the rest.
3. Already in, check out the DataCrystal stuff if you haven't. And I plan to build on this in future chapters.