IMO, 90% of what a new SAA needs is just to be cycled to mate the parts. They're not exactly complicated mechanisms inside, and excessive polishing can affect timing unlocking and carry up. Reducing spring force may soften up the action's feel, but at the expensive of certainty of operation, and lightening the hammer spring by whatever means reduces reliability and slows down lock time on an already glacial hammer fall time.
Modern bore diameters seem to have standardized at .451" - for Uberti, but chamber mouths can measure .452"-.454" depending on the time of day, and whether the sun is at solar maximum. This "theoretically" has a negative impact on accuracy, but whatever that difference is purported to I haven't seen it. A 255 grain bullet is engaged into the forcing cone before the base leaves the case mouth, so initial entry is pretty well aligned, and the use of a softer alloy helps the bullet to compress lengthwise and expand in diameter as it squeezes into the forcing cone. A problem with using bullets sized to match the chamber mouths is they tend to raise pressure, promote leading, and shoot less accurately than one sized to .451".
While round nose flat points are the cool look for the venerable .45 Colt, a better bullet for accuracy is a Keith style SWC with short nose and broad shoulder that arrives at the forcing cone with more bullet still inside the case. The SWC style is also more destructive to tissue, and tends to "turn in" upon impact with bone, versus deflect away as it likely with anything with a rounded nose ogive.
The ammo makers have done a masterful job of making everyone think they need a JHP or some kind of expensive bullet in every caliber, but the old .45 Colt was bad-to-the-bone way back in 1872 pushing huge lead slugs that generated higher velocity and energy due to lower bore friction, and on impact these bullets would readily deform to to transfer energy.
As for the retracting hammer, the issue is that they removed the "quarter cock" ledge which is the first click, and they were so rude as to take the steel with it so it's impossible to just cut a new ledge. I don't see any mechanical reason the ledge could not have been left.
