First of all, I don't believe there is any "Cats drive to attract 100,000 riders per year".
A lot needs to happen before that can happen.
I certainly agree that it takes a huge leap to go from 60,000 to 100,000.
I suspect that the management is fully aware of what problems they have in handling the 60,000 that they are shooting for. The Osier facilty can handle 60,000, but it requires some real savvy in moving people. Handling 100,000 would be out of the question unless the slumps were evened out.
I would expect that as growth occurs, the patronage curve would look about the same, just higher. That is, current lows would stay low, current highs would stay high. If that's the case, there is not sufficient car capacity unless the old "rider boxes' are used, as they are now on some peak days.
The key of course is to find ways to push up ridership in the slump times and push up ridership from Antonito. I'm pretty sure those things are being addressed.
Obviously, Two trains a day is not on the radar until more engines and cars are available. Then you need to have sufficient extra ridership to justify the enormous cost in cars, engines, crews, sidings, etc. Where, when and how would trains pass, turn around, etc.