The buy of 10 (I must admit, I thought it was originally 12) is based on the fact that the T6 will have something like 98% serviceability. Considering these things are going to be parked on the old 203 Sqn line and therefore subject to a lot of salt spray, I find that most unlikely. Also, what happens when a student does a heavy landing and CAT 3s the thing. 10 is simply not enough.
And what about integrating a slow turboprop into a fast jet circuit? How's that going to work?