Most of the items in your poll are either irrelevant to reliability and performance, or are trivially correctable.
What's most important to me in a bolt is good quality steel, well made and most importantly properly heat treated so that it doesn't fail.
Chrome, nitride, etc etc inside the BC is important to reliable function.
Next would be an improved (balanced) extractor design.
MPI is irrelevant. Shot peening is probably irrelevant or possibly contra-indicated. Gas key screws can be staked in 10-15 seconds with a hammer and punch. Extractor springs and inserts shouldn't be an issue with a properly (re)designed bolt, in a standard bolt they're easily replaceable if need be - and correct gas system to barrel length solves the issue anyway. Don't know that I've ever seen a gas key break or fail so I don't know if forged vs. whatever else is really an issue.