I wondered that myself, if it would be a three track system. Yes land would be the biggest issue, as I would see the street car track being east of the existing tracks.
Currently the parcel to the east that stretches from 2100 S to the streetcar right of way, is owned by Archer and Beck, the founders of Automated Business Products, that was formerly located on that parcel. I'm not sure what is in the main building right now, but I do know that the Rock Church (or something along those lines) is in the building at the rear of the property.
So I am quessing that as of right now there isn't plans to build a third platform, like Fashion Place.
Thanks for bringing up that question. Researching that parcel to the east and realizing that I know the owner of that property has given me some very interesting ideas. Archer and Beck own nearly 2.5 acres right by the transit lines.