I'm not really know about submarine, but isn't there suppose to be a floating drydock that can replaced the submarine propellar anywhere in the world's ocean?
Floating dry docks capable of doing the job exist, but there are not enough of them. They are not self propelled and have to be towed, slowly, to a new location. And you never, ever, want to work in one except in absolutely calm water.
You could probably do the job on a Heavy Lift Vessel, but there are even fewer of them, and all are scheduled years in advance.
Instead of tiles, isn't better if the anechoic coating were made in the form of a rubber sheath that a sub can "wear" over it's hull? this should resolve some of the problem like falling tiles.
Modern anechoic tiles are around 4” thick, a sheath that thick would not be flexible. So you would having to build the submarine hull inside the sheath. Getting the air out from between the sheath and the hull would be harder than attaching the tiles, and if you don’t it will be almost as bad as not having the sheath at all.
Plus you will still have to repair it. Things like submerged cables, anchor chains, and fishing nets happen more often than the Navy’s will admit. Not sure how you would patch a continuous sheath. Replacing a few tiles is easier.
Saying that AIP equipped SSK can rival a SSN is taking it too far i think. But still, AIP is not without it's advantage. SU-27 with radar absorbing paint may not make it a cheap F-22. But it may get them a few kilometres closer to the enemy. But still, i see your point.
All AIP gives you is better endurance than batteries. But you can only get it by sitting still or by traveling at low speeds. Typical ranges are 200 km at 5 km/hour, which sounds impressive until you realize that traveling into even a moderate current can bring you to a standstill. :argue
AIPs are quieter than a nuke, given similar construction. Of course, given the cost of the nuclear reactor to start with, a SSN can easily justify, and has the space for, many more noise abatement features than an AIP equipped sub so the advantage is seldom noticeable against modern SSNs.