Am I undersanding the "Blind Pin" method correctly for permenant attachment of a Flash Hider?

a.  Drill & tap the bottom of the F/H for a set screw.

b.  Install the F/H,  tighten the set screw against the barrel to prevent removal.

c.  Weld over the set screw hole to prevent access to the set screw.

d.  DONE DEAL!

If this is the case..., you would thnk someone out there would offer a Vortex, Phantom or whatever with a set screw already installed!!

If I am not mistaken, Kurt at KKF already does.  You may have to specify it that way, but I am sure he would accomodate you.  I have one of his A3FSMS on my Colt M4 and at least to me it is much more aesthetically pleasing than the Vortex or the Phantom.  He installed mine using the method you describe.  He is a true custom shop...he will build pretty much anything you want within reason.