Concept n_n

From what I have read about the new Russian AIP it is rather more powerful than western AIPs and the critical thing is that unlike with western AIPs the whole worlds ports are already equipped to supply diesel to vessels so the infrastructure is already there for them to operate. With western AIPs you need expensive and complicated hydrogen supply infrastructure to be built, plus all the hydrogen generation and storage equipment/infrastructure.

CO2 can be compressed and highly pressurised and released when on the surface or snorkelling. Indeed you could pump it into cannisters and launch them leaking CO2 and making noise as decoys (the mass of bubbles would reflect sonar signals and give size to a active sonar pulse making the decoy look rather larger than it actually is...

BTW if you want your sub to be able to dive deep, then the internal pressure hull would be more efficient if it is made up of a lot of spheres... that allows higher pressures and deeper diving depths.

Regarding CAS I really don't see radar guided threats as being that serious for CAS aircraft and I rather suspect the main threat to replace the CAS aircraft is the UCAV drone that orbits near the front line with very small guided weapons like a KAB-50, and a Kornet-EM like payload...

Operating well above trash fire altitude... say 10-15km up a single drone could carry dozens of Kornet-EM missiles and 20 or so KAB-50 bombs. Any soft target can be dealt with using KAB-50 bombs which would use precision to make up for the small warhead... which also means it can be used in built up areas quite close to friendly troops without risking friendly forces. For hard targets the Kornet could penetrate about a metre and a half of RHA and from near vertical that would mean roof armour.

An armour/concrete piercing bomb could be adapted too and of course a FAE bomb all guided to allow responsive troop support at low cost.

The main weapon of the Su-25 was the unguided rocket and unguided bomb but GLONASS guided bombs and laser beam riding missiles will be just as cheap and just as accurate or more so. (All IMHO).