I'm not talking functionality here, but quality (i.e. non-MIM, etc.).  For example, many may choose to dump the grip safety and/or the thumb safety for beefier versions, but metalugically and QC-wise is there any reason to change these parts?  What about barrels and small parts like the sear, hammer, etc.?

Another way of looking at it would be, if you were going to carry the gun, what would be the bare minimum that you would replace?

OKay, if I am correct, the sear, the disconnector and the plunger tub are MIM.  I would ditch the sear and the disconnector...in fact, on my new Series 80 NRM I did just that.  I would check the plunger tube for tightness ( I always have bad luck with plunger tubes ) and have it corrected if need be.  Then I'd drop in a Cylinder and Slide extractor ( or equivalent...I just like the C and S ) and a Wolff 18.5 lb recoil spring.  Test for fit and function, fit and refit what you need to and tune accordingly.

I also bobbed the hammer and dehorned the grip safety and rear tangs of the frame then finally reblasted it over Xmas....shoots smooooooth.

I'm surprised there aren't more opinions here.

Plunger tube is no longer MIM. Disco, Sear, Mag release.  You won't find a pistol close to the price range that has less MIM. K is chock full O" MIM compared to it. So is SA.

Buy what you want to, but if you want NO  MIM, be prepared to spend 1.5K+.