Being a Lionel purest of sorts, I doubt you would go for a non-original mod over repair, but others might, especially on beaters. The mod is "free" too.
I took a different route on some engines. Taking a cue from the 655, if a boiler looses it's markers, I drill two holes in the face/door. It's the easiest way to add lighted class markers The lenses (not really needed) are Testor's canopy cement, great for making custom lenses and odd glass.