The responsibilities of office require that the  POTUS must always have a de-facto presidential office at his disposal.   Since he is himself is critical of the expense of Airforce One, he should as his next executive order instruct the acquisition of Federal Motor Pool One (aka FedMoPo 1.) I don't think he'd betray his followers, or taxpayers at large, with a modest but secure motorhome, as long as there were no gold plumbing fixtures.