^ not sure about the debt, but the money for the new loop would likely come from the endowment. Translink definitely won't be contributing to it, that's their way of giving the university a middle finger for building a sub-par facility for them to use.
Ideally, i'd like to have a two-level transit station. The first underground level would be the bus platforms, ticketing concourse for SkyTrain, waiting area for buses, and from the ticketing concourse/waiting area for buses there would be a mass of escalators and staircases to the second underground level - the SkyTrain platform.
Inspired by the MTR.

...except both levels there would be train platforms. :p
The 7-platform bus terminal COULD work but ONLY IF SkyTrain (and NOT LRT) is extended all the way to UBC.