Not trying to wet-blanket things but the main reason for my having a Glock 20sf is because it didn't need gadgets and gizmos. If you are shooting a lot of cast bullets, I could see a standard rifled barrel but adjustable sights?? 'they aren't generally target pistols. From your list of goodies and obvious expectations and budget, you are getting up near the cost of an RIA 10mm 1911 type and one of those would be easier to aftermarket 'till your heart's content. Just on what can be done to 1911 trigger alone over any Glock, makes "paper" accuracy more obtainable.
just my .02 YMMV