One thing that surprised me is construction pace of Bykov-class patrol ship. They are being built at decent speed. One of the reasons for it is probably lighter equipment load but whatever.
This production speed opens up some options that I was not expecting earlier.
While they can't use these as platform to build true multi-role ships what they definitely can do is to order dedicated anti-sub version. They just need to add bow sonar, towed sonar is already available as well as helicopter. 8 anti-sub missiles fit in 2 containers and maybe AA VLS behind main gun (if they feel like it but it's not a dealbreaker). They can probably even squeeze in Pantsir somewhere, who knows...
With this they would get replacement for older dedicated anti-sub corvettes. Also with 2 month endurance they would be able to go on patrols for very long time which is handy since you don't know where subs are unlike land or surface targets (so Karakurts can get by with 2 week endurance without an issue, they don't have to look for their targets since someone else does it for them)
Having anti-sub boat roaming submarine bastion for 2 months straight would be pretty neat.
Given the production speed of Karakurts and Bykovs they would be able to replace entire fleet of old missile ships and anti-sub boats 1:1.
This would allow Russia to create very thick padding of their home waters with fresh ships and free up all larger ships for long distance ops.