Does that reveal subs while they're sitting on the carrier though? I was wondering if it's possible for them only to reveal subs when performing an active search mission - perhaps with a limited range, or only a probability, at that. I know the latter two would require the SDK for sure.
I think detection is one of the two problems with submarines right now - the other being their method of attack. Submarines' standard attack should be a "torpedo strike" mission similar to air strike with aircraft (and interceptable by destroyers), replacing the role of aircraft for late modern naval combat -- which don't serve the same role as they did in WWII.
Neither of these is likely modifiable at all until we can modify the game code itself, but I've been mulling over modern naval combat and how it might be done.
There's been five key phases to naval warfare that I can think of: ramming, cannons, metal hulls, aircraft, and missiles. Through most of them you have the basic rock-paper-scissors classifications of capital ships, escort ships, and cheap attack craft to take on the costly capital ships. Submarines and carriers in the game are sort of hybrids.
During the period of dreadnaughts in the metal hull era, only the richest navies could build the huge, heavily armored ships, so other nations developed inexpensive, fast torpedo ships to avoid the capital ship's larger guns and deal significant damage with little risk in cost. This naturally evolved to submarine warfare later on, but in the present day submarines don't fill that role -- they're often as expensive (or sometimes more so) than the bulk of surface ships. In this era the largest threat to warships is small coastal craft (highlighted with the USS Cole attack). Most naval deployments are near the shore, so cheap attack craft armed with guns, missiles, or other weapons can pose a serious threat to expensive warships stationed nearby.
Carriers were capital ships during the aircraft era of WWII, but a different class entirely in the missile era -- relatively ineffective for ship warfare (ship-based missiles are generally better) yet highly important to defend.
The modern capital-escort-attack classifications in game for the late modern age would then be Cruisers - Destroyers - Gunboats. Carriers and Transports would fit in a separate category, as transports for air and ground forces (respectively).
Submarines, though, are a class all to themselves. They're not capital ships that need a fleet to defend them, nor escorts (can't defend other ships against missile attack), nor the poor-man's solution for taking on capital ships. They defy all attempts to fit them into a simple rock-paper-scissors classification!
So I was thinking (with the SDK) Submarines could replace the figher's anti-ship role in the late modern age. WWII-era Fighters can Air Strike ships -- Submarines would have a similar capability (likely a Missile Strike). Destroyers would intercept subs just like their aircraft predecessors. Jet Fighters would then receive a Sonar Buoy order for active detection, revealing subs in a 2-tile fat cross radius around a target (replacing the Destroyer's passive ability). Subs could still attack straight-out, leaving them vulnerable to damage in combat but allowing them to take out relatively unprotected carriers or transports after the fleet has been delt with.
This would all obviously refer to a unit called an Attack Sub or simply Submarine, with Ballistic Subs or Nuclear Subs designed solely for carrying tactical nukes (SS boats can also be nuclear, so Ballistic Sub or Missile Sub would likely be a better name).