Perhaps modeling after the Koreans numbers would be a better choice.
Canada is looking to purchase up to 12 new subs, while less than Japan is currently running, a continuous build could be maintained here in Canada. 1 sub every 2 years apart and flexibility to increase production if necessary, factoring in attrition.
The obvious advantage of the KSS3 is the low crew numbers to operate and high automation.
Getting them to Canada could be an issue though.
Our subs are nearing the end of their useful lives without costly upgrades and time out of service.
Time is running out to get this right, do we put all our eggs in 1 basket?
At best, Canada might be able to engage in a continuous sub building programme, but there would be a very large pile of caveats involved.
I would also hazard that Canada could not realistically start a sub-building programme now which could replace the current RCN subs in a reasonable/useful timeframe. More likely Canada would need to have at least some initial subs built overseas, and then a Canadian yard might be able to get sub construction underway.
One set of issues is just how many subs are realistic for the RCN to acquire and operate, and over what timeframe? Even if someone were to give Canada four new subs tomorrow, it would take some time for Canada to transition over to the new class. If deliveries of a new sub then started at two year intervals, would Canada be able to get enough submariners trained to operate the "up to a dozen" subs in 16+ years? One needs to keep in mind that in tripling the number of subs in service, more than triple the officers and crew would be needed. Not to mention that the RCN would likely need more/expanded/new base infrastructure to fit accommodate and maintain the expanded sub fleet, which in turn would mean even more RCN personnel would be needed to operate, maintain and protect the base expansions. Nothing which cannot be done or overcome, but these are all things which would require time, money and resources.
As for maintaining a continuous sub build in Canada... That would be dependent on a number of factors, like total fleet size, what the construction and commissioning rate would be, how long Canada would keep subs in service and perhaps most difficult and important, whether orders would continue to get placed for more subs through successive changes in gov't. Given the whole debacle with the CH-148 Petrel and CH-149 Chimo acquisition, as well as following gov'ts approach to Canadian defence acquisitions, it is not too hard to imagine that a long-term domestic build programme would get axed following a change in gov't.
Looking at how Japan maintains a continuous build, they commission a new sub roughly every year. and manage this by decommissioning subs roughly every 18 years whilst keeping roughly 24 in active service at any given time. Excepting HMCS Chicoutimi, the
Victoria-class subs have already spent more time commissioned in the RCN than the JMSDF normally keeps subs, never mind the additional time these subs served in the RN or were tied up alongside. If Canada can get things to a point were the RCN can sustain operating a respectably large number of subs, then looking into a continuous build might start to make sense. At present though it looks like such an attempt would be more likely to fail, and expensively at that.