There is sort of a mechanical genius/simplicity/ballet of parts the way JMB designed the 1911. One piece holds in the next and that one holds in the next then the last piece slips in place and it is secured in place by the firing pin and firing pin return spring that went in just before it. Can't do that with an external extractor.
Woody
And if left as JMB designed it to be, all one needs to disassemble the pistol for maintenance or repair is the rim of a .45 AUTO cartridge. One starts by using the rim of the cartridge to remove the grip screws...Most of the problems with the 1911 pistol can be traced back to the humble grip screw. Not satisfied with what JMB gave us, we feel the need to dress our 1911 up, and that often begins with changing out the grip screws to something with a Phillips Head or a Hex screw or some such fancy thing that now requires a special tool. Then, still not satisfied with an already fine single-action trigger, we think we need a lighter trigger so that we can be a better shot, and so we seek to improve upon JMB's design with all manner of trigger jobs and sear spring bending and the changing out of springs and such. Then we often have to polish the feed ramp and throat the chamber so that we can use expensive hollow point ammunition, because rather than improve our marksmanship and work with a cartridge which already pokes a hole approaching 1/2 inch in our adversary, we seek to have a cartridge which will "cover" for us if we can just manage to "get close" with our hits, although it may not always feed properly or work well with our simple, yet quite functional magazines. So then we "improve" and re-design our magazines for that expensive hollow point ammunition, yet they are often finicky and difficult to maintain in field conditions. Then, still not happy with the G. I. Guide Rod and recoil spring, we decide that we need a FLGR, and another special tool so that we may continue to disassemble our pistol. Then, because we are scared to learn that our pistol will work just fine if we will only follow the instructions for cleaning and lubrication, we tighten the tolerances and put on fancy sights so that we can sometimes shrink our groups from the bench by fractions of an inch, yet these tighter tolerances can often lead us to malfunction city. And now, frustrated by a no longer very reliable pistol which started life as a simple, effective tool, we sometimes find our "1911" is no longer as JMB designed it to be. So, we think...maybe if we make it with an external extractor, it will work better. Or, we just give up on the 1911 and get a Glock. After all, a Glock doesn't have grip screws, which as you can see, will lead us down the road to hell and ruination!