If he is going to do it, he needs to go all in or not at all and remove any roadblocks to his agenda.
While obviously we don't want him to suspend the Constitution, he should by decree, find a way around its limitations so he can get done what he needs to. Treat this like a full terrorist invasion.
He should declare a Order of the President for the Protection of People and State
First, suspend Congress. If they are not in session, he will have a valid reason to pass through foregoing powers, any laws and budgets he deems fit to get this done.
He then needs to look at various members of the press and institutions as enemies of the State and not only suspend any license, going so far as to arrest them for aiding and abetting the enemy if they continue to promote fake news.
Due process should be put on hold as judges and individual, local prosecutors or even police forces may be inclined to oppose what needs to be done. Power for prosecution should be centralized within his cabinet. This will also allow for fast export of anyone suspected of being an illegal or fast detainment of those who aide them.
In order to stop leftists from getting in the way, because you know from experience how they 'protest' they will block roads and equipment as part of the wall building process, the right to organize and assemble should be suspended. That should also block union organization into the construction companies and stop any interference by them.
He should also suspend the privacy of mail, telephone, and internet communications communications. Warrants for House searches, orders for confiscations as well as restrictions on property, are also permissible beyond the current legal limits.
Do it once and do it right. Don't piddle paddle around with half assed emergency measures.