You could use one of the 650b tires, like the WTB venture or resolute. It'd lower your BB a fair bit, but it's not like you'll have to clear any singletrack log-overs
the stock rims are 40mm internal. I would not use a tire narrower than ~2.5”. A narrow tire on such a wide rim has very vertical—even less than vertical—sidewalls. Easy to slash sidewalls, more rigid, less cush, easier to pinch flat.