Re cradle failures, see pic
Barrel manufacture is far more complicated than the way you've described it Colin, but essentially it is correct that Canada's order would be too small, and unique, for anyone to want to make just the barrels, or piece meal components.
There are manufacturers that would certainly want to sell Canada a complete system, but far as I know there is no project being created to support that. More mortars might come, maybe, but even those are not a priority (IMO they should be, and they should go to the infantry - this is discussed ad nauseam elsewhere on this site)
The rebuild work can be done by gov't workshops, but it is a matter of priority of work, and having the accurate engineering data (something that is also a problem for the C3), and parts
For example, while the recoil might seem simple, it is tricky enough that the rebuilds being done by the Fleet Maintenance Facility in Esquilmalt, often get it wrong. Even for something that has well documented design specs, it can be problematic if no one can make critical components. Due to scarcity of seals for the C1, it made it necessary to create a hybrid version of the C3's recoil system for the C1 being used for avalanche control. With the problems, and shortages, for the gun's recoil system, plus carriage failures (besides the one that snapped in two in Gagetown, two others had collapsed trail legs), the C1 quickly divested itself and the C3 is now doing the same thing
The US have offered their test facilities to determine causes of failure, and potential failure, but the critical component remains the barrel.
Which does make the OP question relevant. Should the C3 quickly divest itself, then it might mean some of the LG1s being deployed for avalanche control. LG1 were used briefly in 2011 for avalanche control, although not ideal since the spades don't fit the gun rings there. Nevertheless, should it become necessary for the LG1 to be used for avalanche control, again, it would be sensible to train P Res Gun dets in 3 Div on the LG1, (including the unit the OP intends to join), since they typically augment the 1 RCHA avcon dets the most