It only seems feasible to me to have 2 seperate trains. One a people mover on 5 min intervals and then a seperate West rail line running on 15 min+ intervals.
Since the airport doesn't want to build park and ride lots for CATS, then it doesn't make sense to terminate the line at the airport.
It would be nice to have the West line go directly to the main terminal just like MARTA in Atlanta, METRO in DC, and BART in SFO. It looks like our arrangement will be just like Newark, where you have a free people mover running on 5 minute interals that takes you from the main terminal to the parking decks, rental car places, and then stops at the Commuter Rail line at the edge of the airport.
Keep in mind that Amtrak plans on making the Airport a stop in the future for the Crescent and any future high speed rail just like at the Newark Airport.