If he doesn't mind the liablity, both legal and moral, of overweight gun-show losers accidentally shooting (translation: murdering) innocent people, then it's a great idea.
The problem would be one of intelligence, and being certain that the people who were being targeted for killing are ACTUALLY terrorists. If the U.S. military had actual proof of terrorist activity, I don't think they'd want to take a chance on some thrill-seeking tourist screwing it up for them, but would want to take care of business themselves.
I can imagine LOTS of tribal disputes in Afghanistan and other parts of the world that either side would be happy to resolve by "informing" on their suspected "terrorist" neighbors so that gullible U.S. Navy SEAL wannabee's could show up and kill them.
My guess is that any attempt to actually implement a "business" like this would land people in horrible thrid-world country prisons.
The idea is great in principle, and woudl probably have lots of takes (beyond the gun show posers) - but I don't think there is any realistic way of implementing it.