A move from the existing station will not save any $$$, and in fact will cost. The FEC will be happy, eight less moves over the Iris X-ing.
Trains will have to be ready for release from the yards at least an hour earlier, and arriving trains not available to the yard until same later. If the FEC has traffic to move, add to that hour. So far as movements go over the X-ing, Tri Rail is "more or less" on time, Amtrak?????
Concerning passenger convenience, only passengers who wish to use Metrorail to/from final destination and those desiring to rent an auto would benefit. Those who are being picked up or dropped off by private vehicle will definitely be adversely affected; parking is free at the existing station; hardly so at MCS. Taxicabs may have to pay an access fee to MCS or the Airport; that of course means passengers will pay access fees; not so at the existing station.
The objective under the Anderson regime is clearly to operate the LD's as economically and efficiently as possible. I recognize and respect that many here hold making the product attractive should be first and foremost, but apparently Amtrak's record $1.9B "haul" appears to be more related to that Amtrak's FY17 deficit
is probably, adjusted for inflation, the lowest ever recorded over the now past 47 years than to the quality of the LD product.
All told, there's "nothing in it" for Amtrak's operations; best advice, just stay put.