Let me be clearer. There is an obvious gap on the map between Pueblo and La Junta.
Definitely a visual gap in the network that sticks out, and it might be workable. But a key question is if there would be enough demand to justify adding that connecting leg to the Front Range corridor.
Based on the Southwest Chief schedule, the potential Front Range trains to/from La Junta that would connect with the West (for example Denver with Los Angeles) would run in the middle of the night. Not many local corridor passengers in the middle of the night to serve, so that's kind of a non-starter to run a mostly empty overnight corridor train to serve connections.
A connection to/from the East is much more workable. Here's a rough potential schedule for 3x/day on the Front Range (including 1x Cheyenne) with one trip down to La Junta to connect with the Southwest Chief, The connection to/from Kansas City is shown as well.
Southbound
CHD | 605 | | | |
FCC | 710 | | 1235 | 1630 |
DEN | 840 | | 1405 | 1800 |
DEN | | 910 | 1425 | 1820 |
COS | | 1045 | 1600 | 1955 |
PUB | | 1145 | 1700 | 2055 |
LAJ | | | 1830 | |
| | | | |
LAJ (swc) | | | 1929 | |
KCY (swc) | | | 653 | |
Northbound
KCY (swc) | | | 2242 | |
LAJ (swc) | | | 749 | |
| | | | |
LAJ | | | 900 | |
PUB | 605 | | 1030 | 1600 |
COS | 705 | | 1130 | 1700 |
DEN | 840 | | 1305 | 1835 |
DEN | | 915 | 1325 | 1855 |
FCC | | 1045 | 1455 | 2025 |
CHD | | | | 2135 |
These trip times are roughly in line with what Connect US aims for and they seem to not only offer a good hookup to/from the SW Chief but also useful times up and down the Front Range. So it's definitely possible that a reasonable Front Range schedule could also offer connections at La Junta to points east. (Like any speculative schedule, this is subject to hurdles like the cooperation of the host railroads, logistics of crews and maintenance rotations, etc. but for this discussion let's assume those are workable.)
Note that this schedule would also connect to the California Zephyr in Denver as well, but only to/from the East. It could be adjusted to connect to/from the West available by making the early-morning departures out of Pueblo and Cheyenne be at about 5am. The evening departures out of Denver would probably need to be pushed an hour or so later to have a good shot at routinely allowing connections coming from the west, too. And there lies a core conflict when it comes to all these new corridor train proposals. They are primarily to serve local traffic between the key points on the corridor. How much do you design them to connect to the LD network, knowing there's risk of harming the local demand? Pushing those morning inbounds an hour or so earlier (roughly 5am instead of 6am out of Pueblo and Cheyenne, 6am instead of 7am out of Colorado Springs and Fort Collins) will probably cost at
least a little traffic. Is that acceptable? What if it needs to be adjusted another half our earlier to 430 and 530? I love connectivity as much as anybody, but the corridors will probably live and die by how successfully they build traffic within the corridor itself, and if ridership is stunted by schedules contorted to allow good LD connections it risks the route failing.
Back to the topic of extending a train down to La Junta to connect to points east on the Southwest Chief. It 's workable, but is it likely to draw enough ridership to make it worthwhile? Who would ride that extra leg? There would be some local traffic served between La Junta itself and Denver/Colorado Springs/Pueblo but La Junta is a pretty small place -- in 2019 it boarded just under 5 passengers per departure on the SWC. This added leg would mostly be there for connections. But connections to where? Kansas City is the only significant market it would open up because the rest of the stretch between La Junta and Galesburg (where it overlaps the California Zephyr) is dotted with points which board a handful of passengers per departure. So the bulk of passengers on this new La Junta leg are probably going to be to/from Kansas City.
Kansas City-Denver is a sizable market though it's hard to estimate how large ridership would be for a direct KCY-DEN train -- potentially a lot, especially a daytime train where coach is a decent option. The concern I have about how many passengers Kansas City -Denver would attract via the La Junta extension is that it is substantially longer than alternatives, overnight, and requires a change of trains. I'm not one to say trains must be nearly as fast as the car, but I do think it has to be "reasonable", admittedly a subjective term. Driving Kansas City to Denver is about 8.5 hours, and a direct Greyhound does it in just over 11 with stops, including a daytime option. Amtrak would take over 15 hours overnight and require a connection. I doubt it would attract many passengers -- probably a tiny fraction of what a daytime train would running a more direct route. Can't really guess how many it would be each day but it would not surprise me if we're talking a few handfuls at best per train. And because that is the backbone of what would justify the La Junta extension, I think it's a tough sell.
If the Southwest Chief is rerouted to run through Pueblo that's largely a different story. Connections could take place without any added cost of extending the Front Range route. Not knowing what sort of times the train would pass through PUB it's hard to speculate how well schedules could mesh, and there is the same concern where you do not want to sacrifice local corridor traffic by scheduling inconvenient times in the name of LD connections. But should it reroute through Pueblo that's probably a much more plausible way to link Denver to the Southwest Chief, as much as I would enjoy seeing a La Junta extension in some ways.