When the SLSTA originally restored 1522, there were some hand wringers who were outraged over us replacing the brake system with 26L, adding a second lubricator, installing an electric speedometer, EOT receiver, modern radio, MU box and the temp monitoring system. We were absolutely ruining the engine.
Well guess what? Having done all that made the engine feel comfortable to the pilots, soothed the worries of the supes and higher ups. Plus the fact that the brake system used parts that were available at any terminal. We always had a spare brake valve and it saved us once when ours popped a leak. We stopped between switches of a passing track on the BNSF at West Alton and were moving again in 40 minutes with a new brake valve.
Original fabric doesn't matter to the railroad, but anything you can do to make it fit in with traffic does matter. Do what you gotta do.

I think that the 4501 is a shining example of what is required to actually operate steam in the modern environment. Since we are not building new steam locomotives which comply with current interchange standards (roller bearings, etc.), we must bring the old ones up to something approaching modern standards if we are to have any hope of actually operating on the general network. Old locomotives, if they are to remain "old" are simply never going to comply with the current safety and reliability standards in force on todays railroads.

If a lion in the zoo is to be released into the wild, it needs to be healthy, robust and strong enough to survive among its peers. Otherwise it needs to remain in the zoo where it can look like a lion and act like a lion but in a safe and controlled environment.

No sense complaining about the "compromises" being foisted on the 4501. We need to be happy that 4501 is being given the strength and health it needs to be able to live in the wilds on the main lines!