I would have to wonder what DND standards are? Heavy Duty Mechanics (offroad/ Highway)may specialize in certain machine types, But engines, drive systems are similar. If you can fix one you should be able to fix them all using the manuals. (I know each have their own tricks)Seem to remember that this was suggested in mid 80's but reversed, Take a qual diesel mech convert them to DND stds BUT retain the origional cert. Not sure where it went tho.
For electro drive, sights electronic things you need to specialize, there are instrument techs who if you pay them they will fix it for you.
Overall the military needs to stop thinking their equipment is so intricate and hard to fix that only they can do it.
Start looking at more third party overhaulers, and get them involved. Does the Canadian Military overhaul their own engines and transmissions, or do they use a third party? What about their electro/ mechanical devices?
I know the Airforce had the capability to overhaul some of their avionics and engines/ apus. But much of the work was third party. The front line guys diagnosed and changed components. Sent the assemblies away for repair often.