The B word
I would agree with your logic, the Viking is a low cost recovery for an airframe that is next to worthless in terms of resale value due to the uncertainty of its type certificate.
The Vigilent has a civil type certificate holder and so the task of civil registration is relitivly straight forward and the aircraft will have a resale value to match, it also requires for long term operation an engine retrofit that will be expensive.
In terms of cost to return to service for the long term I would take a stab at one Vigilent will cost the same as five Vikings.
It is my opinion that the Vigilent is not giving the cadets the training value for money that the Viking can at a much lower price, I am a great advocate of real gliding because it builds a team who fly, recover and launch the gliders, you don't get this with motor gliders because before as a prop starts to turn the cadets have to be the other side of the fence in the Crewroom.