None, I think.
Personally, I only want to see troops doing things that physically put a stop to the invasion.
Actually building real barriers would be one. Active patrols would be another.
The US government has enough bureaucrats to do the paperwork.
I like AZ Governor Candidate Goldwater's idea of setting up tent cities along the border to house convicted illegals and then offering the early deportation for building the security wall that Bush and the Feds refuse to produce.