It would be wasting good, and very expensive brass. You might get more reloads out of it, but not enough to cover the additional expense. You always have the option of loading down 454 as opposed to cutting down the brass.
When I was doing Cowboy Action shooting about 16 years ago, I was using 7.4 to 7.8grs of Unique with 200gr Lasercast bullets. Made for a comfortable shooting cowboy load.