A few thoughts:
From a ridership standpoint, keeping the SWC on the Raton Pass route only makes sense in that it: 1.) Serves Albuquerque with a downtown stop and 2.) Keeps the possibility open for the route to connect to the Front Range. IMO, if the SWC doesn't get rerouted to Pueblo or otherwise connect to the Front Range via rail, then it should be rerouted to Amarillo (which is an ideal candidate for Amtrak service).
The Pueblo metro area is also in the sweet spot for Amtrak service (150k people without convenient airline service). Yes, a detour would lengthen the SWC's running time, but the ridership boost on the otherwise sparesley populated ABQ-Topeka segment could make it worth it. Also, Pueblo is arguably the best candidate for where the SWC could connect to a Front Range rail line (this is proposed by the Colorado Rail Passenger Association:
http://colorail.org/wp/wp-content/uploads/2014/12/ColoRail-vision-map.png)
Discussed in a recent ColoRail meeting, another benefit of a reroute to Pueblo would be more convenient access to the tourist railroads in the southern part of Colorado (especially if the SWC stopped in Walsenburg). This could help boost the economy of southern CO and improve ridership on the SWC.