My quick take on the situation would be we would need another train set of about 10 cars. This set would probably get somewhat divided between Chama and Antonito giving us around 29-30 passenger coaches/restroom/snack cars. Two trains would run out of Chama when business dictated, each train being about 12 cars - including snack car and gon.
Schedules would have to be staggered so each train would arrive at Osier in a matter that would allow each train's passengers to be fed without over- running the facility. Obviously the Osier Loop is a necessity.
The current format works well with 5 fully functioning locomotives. To add another train using the well used formula of 1 1/2 engines per job (rounded to the next highest number):
3 road engines
2 helper engines
5 total X 1.5 = 7.5 or 8
We'd need 8 engines, but could probably make due with 7 because the 2nd train would necessarilly be doubleheaded every day its used.
We have found over the years as business grows the the hills and valleys of patronage begin to fill in. The big days get bigger but the slow days fill in more. The is perhaps a function of local lodging capacity forcing patrons to days of availabilty.
With some careful planning, Osier could handle about 400 passengers a train. If more gets dumped into the mix at once, expansion would be needed.