He should discuss the potential impact on his career with the base legal office. I doubt that the military would smile on his conspiring to help you stay in the U.S. in violation of immigration laws.
As you probably know, there's a risk in entering the U.S. as a tourist, getting married and trying to adjust your status, as when you enter as a tourist you represent that you have no intent to immigrate. The risk is that the USCIS may decide that was a fraudulent representation made to enter the U.S., justifying deportation and a bar against reentry.

