The Redhawk Alaskan sounds like it would be perfect for what you want. 44 Mag is plenty unless you are stepping into grizzly country. 454 is a beast(but a great round). I have a Super Redhawk in 454 with a 7.5" barrel, and it pounds you hard. After just 3 or 4 rounds, I can feel my wrist starting to hurt. I have let numerous people run a cylinder of full power loads through it, and no one has requested to try more. One guy said "I was wishing it was over by the 3rd round". But yes you can shoot 45 Colt out of it for light loads.
I also have a 460 (BFR) and yes you can also shoot 454 and 45 Colt out of it, but I have found that accuracy suffers significantly with 454 and 45, so I just stick to 460 rounds now. That gun is really heavy, so recoil isn't as bad as the SRH in 454. It has a bigger push, but not the quick snap of the 454.
Skip the 460. They are massive guns and not nearly as handy as the Alaskan. You really can't go wrong with either the 44 or 454.