I just happened to stumble onto the Indiana change from a couple years back to the firearms season. The change allows legal calibers of 35 and larger. The case maximum length can not be longer than 1.625 inches and not under 1.16 inches. This basically includes the 357 Mag. up to a 500 S&W however a WSSM case necked up to 358 can fit the requirements.
Custom guys are sizing up the 25 WSSM case to .358 with a small trim in the neck length for just this very purpose. Remington does have basically a 30 WSSM they call the "30 Remington AR." There is also the 30 OSSM from Olympic Arms. It might only be a matter of time before someone manufactures a 35.