Any reason why the STX 85 couldn't be armed like a corvette and some sensors added?
Then it becomes 80% the cost of a frigate, so what was the point of buying that small (supposedly cheap) 2000t OPV?
You are forgetting that the two largest costs of a warship isn't the structure and the fuel costs, or even maintenance (unless is is an intensive nightmare). The two largest costs are the systems and the through-life crewing requirements.
EDIT: I assumed that by "armed like a corvette" you mean a 57-76mm gun/SSM/PD-SAM(such as ESSM)/(optional CIWS)/helicopter capability.
My plan for a cost effective Canadian defense was a mix of three long range AIP subs per coast operating two at a time for patrol and five OPV per coast backing them up closer to shore and or performing any boarding of vessels.
You cannot sustain that kind of patrol effort over a long period, even if you are going to multi-crew the subs. The vessels/crews need time to maintain, train and regenerate effort. You can't do that with 2/3 of your subs always at sea.
COMMENT EDIT: I understand where you are coming from with your ideas. Like many Canadians (and others around the world), you see the military coming back from long operational commitments and associated military expenditure and reassessing defence needs in light of uncertain economic conditions. You are looking for a new peace dividend.
Canada is in a fortunate security position in an area of low external, conventional threat. As such you are looking at what Canada
needs to defend Canada and no more; Gen4 fighters (Gripen NG) to police air space, smaller vessels for EEZ patrol and national defence and some larger support vessels for token humanitarian relief.
But this ignores Canada's broader national interest and international commitments which isn't served well by 2000t OPVs and (arguably) Gripen.
When it is given up, capability cannot be gained back quickly when it is required.
The easiest capability for a nation to commit is transport aircraft and warships, but they aren't going to commit an OPV to a potentially hostile situation (such as a renewed
Tanker War) and once you get rid of your frigates it can take many years to get them back again.