Before they built the loop, I always wondered why they didn't put in a wye just to the west of Osier. It looked like you could run legs up into the creekbed ("Osier Creek"?), since the mainline makes a sharp turn to the South to get around the mountain.
When we we hiked over to Toltec tunnel earlier this year the kids asked why the loop looked so "uneven". I told them it looked to me like there just wasn't enough fill. My guess is it would take a lot of work to stabilize the loop on a permanent basis. The fill is tall and steep -- it seems like the snowfall/drifts on Osier would give it quite a shove each year.