They CAN, but there would be no going back and the benefits would be minimal imho.
The regs are inserted into the tube and a breather hole drilled. They take air volume from the tube and after drilling, you would not be able to use that tube without a collar or reg inside..
The only other alternative I know of would be cutting and threading the tube to use one of the CR series type regs.
These can be tuned pretty well so what would the gain be For installing a reg?
In addition , you're adding a likey point of failure to an incredibly reliable rifle.
Just my thoughts.
Nice rifle , btw!
Bob