From all accounts the Twin Otter is a very good aircraft and I don't doubt that good use could be made of it in the CF. The Arctic in particular looks like it could benefit from such a platform.
However, it's becoming clearer to me that like every other thread which proposes a new and useful platform (Corvettes, Bombardier MPAs, F15-X / F-35 split fighter fleets, converted commercial "Big Honking Ships", light attack aircraft, etc.) that while a good case can be made for the proposed platform/capability, the cost in additional support, training overhead, staffing requirements, logistics tail, etc. is argued to be too much for an already thinly spread CF to support without cutting into other, existing capabilities.
No doubt there is fat in the CF that could be trimmed to free up budget space, but as has been mentioned by others before perhaps the only real solution is a proper and full defence review to determine (REALISTICALLY) what the CF is expected to be able to do within the budgets that the governments (of both stripes) appear to be willing to provide.
Only then can the CF be properly organized and equipped to fulfill these capabilities. Anything beyond that should be left to other departments if they are required (or new budget specifically added if there are new CF requirements added). Until then we'll likely try to keep our fingers in every capacity at every level and not be able to do any of those things really well.