"Location, location, location..."
As a general rule, all roads in the USA lead back to the 1911/1911A1. Its manual safety was placed just right to be a "thumb safety" for right-handed operators, and it serendipitously was also a clever bit of working (yet another) safety into a jigsaw puzzle of components back there at the back of the pistol. The actual interface with the thumbs of many people sort of sucked for a long time, but nowadays about anyone can find a version that works with their own issued thumb(s)...
...at least to push the safety off. Activating it can still give people a bit more trouble. And over the years, it seems that even practiced users can end up with a cocked and unlocked 1911 in their holster or waistband or glove box.
But, by golly, it is mounted on the frame!
So is the weird little "lever and button" of the CZ 27 and the oddly inferior - but politely informative - safety of the Pistole 08. Neither one gets much praise from anyone other than buffs and foamers, so "location" must mean more than just somewhere on the frame.
At an impromptu bull session during one of my rare trips to the John M. Browning Museum at the Rock Island Arsenal, a fellow visitor who I did not know from Adam opined that if Walther had set up the safety on the P-38 so that the safety lever had the protruding thumbpiece behind the pivot instead of in front of it, it would be as "instinctive" as a 1911, AND it would provide for decocking. He didn't bring up the potential fragility of the P-38's decocking "bits," and I didn't point it out. I bring this encounter up because, imagine if you will, a world where - just maybe - people would wax poetic over slide-mounted safeties.
In any event, the current state of the art vis-a-vis 1911 safeties is a "golden age," and they work just fine. That being said, I also think that the slide-mounted Beretta safeties are pretty doggone good now too, thanks to some long-time complaints about geometries being addressed. I seem to be able to function okay with either, and I am not exactly deft anymore.