It seems to me that creating several dozen subscription plans on Stripe is indicative of a deeper problem: that you have several dozen different prices consumers end up paying. How about instead you advertise the prices that consumers will actually have to pay? Bump up all of your prices across the board by the expected cost of taxes to even out the cost.
(Unless there's some law about not charging consumers in different provinces a different pre-tax cost, or some province charges so much tax that to make other provinces eat a share of that cost would be unreasonable.)
It's funny how different countries and cultures have different views over the same thing. I'm not sure about Canada, but in the US taxes are added on top of each purchase so you advertise a price of 14USD and end up charging X% on top of that price.
If I understood your suggestion correctly people dealing with these problems should do like we do here in Brazil: use the taxes to compose the final price so if I have a product that I want to sell for, let´s say, 10USD and will cost me an average 10% in taxes I would advertise it for 11USD and just deal with the taxes problem internally in my app and not by creating N different plans on the payment processor.