Depends on the area and season that you plan to hunt. If you want to hunt the ''short range weapons'' areas a shotgun with sluggs or buckshot, muzzleloader, in-line muzzleloader, flintlock, long bow, recurve bow, compound bow etc are legal. I belive durring ''rifle'' season you can use a muzzleloader of just about any type, but muzleloader only seasons require the rifle to be loaded from the muzle, some require no pelletised powder, and have ''exposed ignition'' if I remember correctly. This means NO 209 primers wich rules out most all the inlines. If you dont want to shoot traditional roundball etc, get a fast twist bbl and you can shoot connicles and sabbots. But youll have to look at the regs to see if sabbots are legal.
Ive hunted Idaho a couple times and LOVE IT, but its been a couple years since Ive gone thru the regs. Lyman makes a nice inline called the Mustang I think, and I own the Lyman Plains Hunter in a 50 cal. love it, but Id like to get one with a fast twist bbl so I could shoot maxi balls or sabbots. My current one wont even shoot minni balls, its a round ball only shooter.
I shoot a .490 round ball over 100gr of FFG with a .015 prelubed patch (overkill on powder, but its accurate). I can spin the 3'' spinner gong at 100yds consistantly. And have taken 3 Mule Deer with it. Old school rocks, but an inline of some kind would be a treat for reaching out there in those units that allowed them.