The problem that a pre-positioned Euro Brigade leads to is one of the tail wagging the dog.
Canada is currently structured to supply 3, maybe 4 at a stretch, brigades(groups).
As you state the reality is that Europe is the only place we can use a Mech/Heavy brigade and then only if it is pre-positioned.
It's not the only place. It is "currently" the best place. There are numerous theatres where an opponent could bring heavy armoured forces into play. Some with antiquated equipment others with much more modern. Heavy is a tool you need to keep in your tool box albeit it could very likely be maintained at a much lower level of readiness than special and light forces.
Light or Light/Medium brigades are, in my opinion and I believe in yours, are functionally much more useful to the Canadian government and better aligned with their sense of the threat and Canadian voter's wishes.
I doubt if the government has any real idea what the "usefulness" of these brigades are. It currently has no major strategic mission on the go other than Latvia and that should be heavy - hence - heavy is the most useful. For the sake of our soldiers they should have something more than a cobbled together mish mash of tanks, LAvs and M777.
But if we are manning a permanent presence in Europe does that mean that the other 2 or 3 brigades are merely Mech soldiers in waiting, champing at the bit to do some real soldiering in a garrison in Latvia?
As long as we maintain Latvia as rotational then the answer is, no. They are in a logic rotational cycle and not merely champing at the bit. The real question is: should Latvia be rotational? Or is it that we are stuck in an Afghan model of operational deployments? My opinion is that rotating people and and out of combat is logical and desirable; rotating a deterrence force isn't - it creates sever and unnecessary stress on the whole army.
Or should the emphasis be on training, and employing the light forces in real world scenarios with the time in the mech brigade seen as the disruption to their routine?
Latvia is the real world, but I take the point and agree. Light forces should be training for the light role, and from what I understand they very much are. Latvia is a disruption from that but then again since our mech forces are LAV based there is not a major difference once you compensate for the need for trained drivers and turret crews.
My sense of my era was that 4 CMBG was seen as the real army - 2 battalions and a tank regiment. The other brigades, that could have been actively engaged preparing for CAST and AMF(L) largely seemed to be at loose ends.
There's no doubt that 4 CMBG was viewed differently - you couldn't help it, their establishments of troops and equipment were full. In many ways the training was much better in Canada but in some ways worse because you couldn't do everything in a little Bavarian town on a dry exercise that you could do live firing across Wainwright.
That said, the roles for defence of Canada, CAST and AMF(L) were not at loose ends. They were different. 4 CMBG didn't train for air mobile ops. In Canada we did - and in a big way. Things changed over the decades from the 1970s which were "lighter" then we went to AVGPs and were simulating Europe and, for the guns, when we traded our L5s and went M109 we went even further preparing for Europe (In my case with a flyover battery role). Admittedly the latter 1990s were confusing for everyone.
Trudeau's army reflected his LaPorte crisis experience. He wanted an urban force that the army detested. Rifles and armoured cars that would be at home in Northern Ireland.
Interestingly, In Canada we were already capable of being an urban force in 1970. Our deployment in October 1970 was basically as light infantry - even the artillery regiments. The armoured corps sent Ferrets and riflemen. We did VIP and VP security, cordons - all that stuff. We did it again in 1976 for the Olympics in Montreal and Kingston. No one "detested it". It was a change from the normal routine. Soldiers appreciate that as long as it doesn't become your primary role. It didn't. I'm not a Trudeau fan - neither one of them - but under him some hard-core defence priorities were initiated - the Leopard tanks, the CF 18, the Aurora, and the patrol frigate. Trudeau may have had a different idea of the security posture Canada should take but at least he had an understanding of world politics and the role of a security policy unlike his sprout (or, IMHO, Chrétien)
Beatty's army, because Mulroney saw everything in transactional terms and wasn't committed to anything in particular -
Beatty's army nodded to the urban with the Bison armoured cars for the Militia and also with the Vital Point security forces, but also addressed the control of the terrain not accessible by roads with the planned purchase of hundreds of Bv206s.
Do the home brigades get equipped to train for the Euro Brigade or do they get equipped for domestic and international operations as an air-transportable, Hellyeresque force built on the lines of the ACE Mobile Force (Land)?
I lean towards prioritizing the light role and leaving the prepositioned brigade as lightly manned and minimally trained as possible. But I also want to see that brigade heavied up with GBAD and LRPFs, assets that can also be of value to the light forces and that should be built on platforms suitable for air transport.
I've said this several times - on this issue I'm follower of Guy Simonds who put forward that if you've trained for conventional war you can do all the lesser stuff. The reverse isn't true.
I agree with much of what you say here but again, we differ on semantics. I wouldn't "prioritize" the light forces, but I would have them trained to and maintained at higher states of readiness than the heavies.
Essentially I would turn "heavy" into a 30/70 force of four manoeuvre brigades (1 fully equipped but lightly manned brigade in Europe and three fully manned and lightly equipped brigades in Canada roughly 5,000 RegF and 12,000 ResF) with the role of generating a deployable flyover brigade at rotating levels of readiness.
The remaining 10-13,000 RegF and around 8,000 ResF (in one light [high readiness] and one mech brigade [rotational readiness] and two light coastal regiments [low readiness]) would be fully equipped light to medium forces for all day-to-day defence of Canada and all other deployed operations (which could include other missions to Europe but not generally the forward presence brigade)
(The overall numbers would also include several hybrid combat support and combat service support brigades [at varying states of readiness depending on function])