IMHO/Experience I would say lots and lots of inexpensive Corvette/Frigate/DD/DDG. Something like OHP (One Arm Bandit held around 40 weapons and could fire an ASROC), Spruance (But with much better AAA. Maybe like a Kidd but only 1 launcher). The more hulls and helicopters you have looking for submarines, the better. Helicopters are the only non-submarine weapon that a boat fears. They’re faster than the SS/SSN/SSGN, and you really can’t see them coming. They should all have a towed array as well. An affordable helicopter carrier would be great. 4-6 CIWS down each side. Sea Sparrow (or some type of point defense missile system). I always thought that NATO ships (really looking at you USN) were woefully under equipped when it came to modern AAA.
IMHO many countries didn’t go the nuclear boat route because of the lifetime expense. Everything to do with nuclear power is just so expensive. Just training and keeping operators has been a nightmare for the USN for decades (Current enlistment bonus is $75,000, with the ability to make up to $360,000 if they reenlist 3 times). That’s not the designing, building, repairing, operating, refueling, or overhauling cost.
Putting nuclear armed cruise missiles on subs was a very bad idea. Bush actually removed them all. Neither side wants to have mini SSBNs all over the world.
IMHO think that NATO was way late to the SSGN party. Should have had those way before they did. VLS 688 was/is nice, but more is always better. Maybe they could have added a short section to a 637 or 688 for this. (Of course they would have needed the ASMs to arm them with. Something IMHO the USN is way behind on due to the Carrier Mafia running the USN. Or institutionalized stupidity.)
Most of the above is due to my belief that there are only two types of ships, submarines and targets.