Look at missile boat combat history. They are easy targets for airforces. They are usefull when you can protect them with bigger ships.
Yeah, but that combat history of them being vulnerable on their own is largely based around small boats with small short range sensors and generally armed with not much more than MANPADS in terms of self defence missiles meaning most anti ship weapons allow aircraft of all types to sit outside their effective range and potentially keep firing till they are sunk, but actually most of the time with their lack of situational awareness having them sunk pretty easily from long range.
This ships in comparison will have information from other platforms including subs and satellites and land bases and ships nearby and they will be providing their own information to add to that information bank.
the missiles they could be fitted with would include S-350s or at the very worst naval versions of TOR which means 150km, 60km, or 16km range missiles... which is not very shabby at all.
Modern frigates haveba rcs of a small fishing boat.
Big enough...
There are no invisible stealthy ships as far as I am aware... except submarines of course...
Why you think it will be cheap? Steel plates are cheapest part of ship. Weapons and electronic make them expensive and this ship have asw weapons and equipment in addition to already existing weapons and equipment. So it will have all expensive stuff but in cramped ship without good range and endurance.
All new Russian ships are expected to be fully multi role and multi role systems will be fitted to all vessels... bigger ships have bigger systems incrementally more launch tubes and larger calibre guns, but they all need to be able to do a bit of everything... which means for effective anti sub use you might need a couple of smaller ships to do the job a single bigger ship could do.
Putting so many weapons and equipment on small ship doesn't look rational to me. Warship first have to be good ship. This one will be still small, with very limited range and endurance, but quite expensive.
It wont need long range or endurance if it operates around Russia... but its fire power would release a much bigger boat for other duties further away if needed.
Russia need navy that can go away from shores.
It does but for your average family you might have a motor scooter or two for zipping around town easily and cheaply, while a normal Sedan for a work car for husband, while wife might drive the holiday adventure four wheel drive SUV as a shopping wagon and to go for coffee because its enormous size will make her feel safe.
Why would Russia want scooters with huge saddle bags so you can go on long trips or tours in? Surely you go on long trips in the SUV because you can get all your gear in it and the skis or surf board on top or you get some big heavy touring bikes.
Corvettes are motor scooters... don't try to turn them into touring bikes... a car or even a camper van make much more sense for that role...
ie Corvettes for in and around Russian waters... Frigates too... and Destroyers and Cruisers for further away later on.