Interesting revival of this thread. Let me just address a couple of points.
Sustainability of such a battalion depends entirely on funding. In effect there is very little difference between a Reg F and a Class B-based unit with respect to costs albeit terms of service differ significantly. However, creating a Class B unit is just a way to cheat the PY limitations imposed by the government on the number of regular force personnel. As others have stated, reservist, regardless of class are CF members who are "enrolled for other than continuing, full-time military service when not on active service". That's a legal status and the creation of a unit composed of "continuing, full-time" members by way of Class Bs isn't really allowed although we have for quite some time now run rough-shod on the concept. I'm of the view that for every Class B member you can hire 3 Class A members and properly train AND equip them indefinitely.
I love reorganizing the ORBAT of the CAF as much as anyone, but there are certain considerations to keep in mind:
1. We tend to lose sight of the purpose behind the reserve force structure. For almost a century Militia units were the foundation of mobilization. Militia units in peacetime had much of the needed command structure (both officer, NCO and a core of ORs) so that it could be bulked up by civilian recruits, trained and deployed as a "mobilized" unit. Because of this there were hundreds of Militia units which could conceivably be mobilized into several corps of hundreds of thousands of troops.
Over the years the size of the "to be mobilized force" was reduced and accordingly many Militia units were zero-manned and relegated to the supplementary order of battle. Around the 1960s, with the expansion of the full-time army, the "mobilization" concept faded away and was mostly replaced with a concept of individual and small group "augmentation" to full-time regular force units. At the time equipping Militia units with "mobilizable" equipment disappeared in favour of a handful of training equipment only while all the operational equipment is held by the Reg F.
The reserves, however, still have a structure that looks "mobilizable" with all its COs, RSMs, Coy Commanders etc. If one was to take our current structure (which according to one government website says has 19,000 Army reservists in 185 unit - and I question the accuracy of those numbers) and manned each of those 185 units to a "mobilized" level of let's say 600 personnel each then the Army Reserve could expand to some 111,000 people. We have no plans to do that. If, on the other hand, you want to set up the minimal structure necessary to train and hold those 19,000 reservists based on those same 600 man units then you could reduce the number of units to just 34. We have no plan to do that either.
So why are we structured the way we are? Its basically a policy of sucking and blowing at the same time. We don't want to pay more reservists but at the same time we don't want to offend a whole lot of folks by putting even more units onto the supplementary order of battle regardless of how weak they are.
2. It's a bit hard to aggregate Res F units because they too have a legal structure albeit that this can be changed by the MND as needed. There's no reason what you propose can't be done, but it's more complex than necessary. Effectively what you are doing is part and parcel of the same "suck and blow" shell game that we're doing now through such structures as the always popular "tactical group". Effectively we're trying desperately to keep some old units and traditions alive. The right thing to do is to either keep the structure we have but develop a proper mobilization and expansion plan (which is really something we will never do) or, on the other hand, reduce the number of units to those that can be properly recruited and equipped indefinitely as either force generation units, force employment units or (and preferably) both.
3. The fact of the matter is that our Res F system is an anachronism that is on the one hand fed by a Res F leadership that is hanging onto the past and a Reg F leadership that doesn't want to or doesn't know how to make the reserve force a viable, credible mobilizable force by creating proper system of reserve service that elevates the training standard of the reservists, properly equipping the reserves and providing for its maintenance and properly including the reserve units (and formations) into defence plans. For the Reg F it's always a budget issue, but as I've said many times, I think it goes much deeper than that because a properly trained and organized reserve force would be be less expensive to maintain on an annual basis than a similar full-time. The trick is to determine what forces you absolutely need during peace time and which are only necessary in a major emergency (which for DND by definition includes war)
What's missing from our entire Army reserve system is an overarching coherent plan - in essence a doctrine for the army that full incorporates the reserves in the full spectrum from peacetime to high intensity conflict. We've had numerous studies on the subject which have for the most part either gone into the trash bin or resulted in minor incremental changes. I'm afraid that there is no way that the situation for the reserves will ever improve until there is both a Minister of National Defence and a CDS and a CLS who are prepared to undertake serious reform from the bottom up.