Again, this is a thought experiment as Moncton's Starbucks #8 is still only a rumour, and we really have no idea where in the metropolitan area it will go
but:
If it were to go on Mapleton (which seems plausible), I would think it would be built further out, likely in association with either the Mapleton Centre or Mapleton Crossing.
In the Mapleton Centre, it could be built on one of the vacant pads backing on Mapleton Road (good visibility) or on the vacant pad between Goodlife and the Bombay Company. That particular lot is the ideal size, but is well off the highway (but very visible from Wheeler Blvd). The Mapleton Centre lacks a coffee shop/lunch place and this pad is ideally located in the centre of the development.
In Mapleton Crossing, Starbucks could be located right on the corner of Mapleton and Cabela's Court right next to Princess Auto. The current plan is to have a combo gas station and coffee shop in that location anyway. This is a high profile location in a destination retail development and has the added bonus of being visible directly from the TCH, which could be a major bonus with increased traffic from drowsy drivers passing by on the freeway.