The struggle is to fit a roundtrip into a single day (and preferably: into a 12 hour shift or split-shift). Currently, there are trains like #64, which departs TRTO (11:30) before the first train arrives from MTRL (#61@12:03) and arrives in MTRL too short (17:05) before the last train to TRTO leaves (#668@18:25), meaning that unless you send the LE before or after his scheduled trip on a plane, he will spend one night in a hotel. (Keep in mind that shifts originating at TRTO often start at TMC more than 1 hour prior to departure time at TRTO and that shifts terminating at MTRL often end at MMC more than 30 minutes after actual arrival time - plus any delays).
With HxR, you will have the possibility to let the LE travel back on an HxR train (say: MTRL@19:30 to TRTO@23:30), maybe not just as a passenger, but even as driver…