As much as I've been a lifelong sub nut, the conditions aren't particularly good for a sub yet.
1. What's the purpose of an attack sub?
Stealth munitions ambush on juicy targets: redundant with saltseeker for capital ships, fuzzy GM calculus for logistical targets.
Stealth insertion/extraction of special operations forces (SOF): we don't have SEALs (yet), fuzzy GM calculus for SOF raids.
Stealth recon and SIGINT/ELINT collection: SIGINT and ELINT still aren't a thing (yet), fuzzy GM calculus for recon in general.
2. How do you find an attack sub?
Lots of small boat for patrolling and escorts: guess who has lots of small buccaneer boats with nothing better to do now.
Helicopters lowering hydrophones into the water: they have helicopters that could be revised for this.
Active Sonar: probably would need a full design at least.
3. How do you sink an attack sub?
Depth charges: a timebomb that sinks would be a trivial revision, plenty of small boats or helicopters to drop them from.
CAS ambush while on surface: diesel electrics need surface time and at least they really don't have a CAS or Naval bomber
So yeah, as much as I'd want a sub, we need to at least corral their small boats with a GOOD destroyer or our own small boats. Otherwise our subs just won't have the open seas they need to operate.
In order:
1. The Saltseeker is outranged by the Cannalan Stingray, which is also cheaper, faster and has a better hit rate. We are losing in ASM pretty badly right now, which is why Naval Advantage went to Cannala instead of neutral. So we can't hit their capital ships by saltseeker.
We didn't have Salamander Marines, or the Cannalans their Aswang commandoes/ptero pilots before we invented those things. Unit designs are out of the scope of the game. And SOF raids have been stated to affect battles numerous times, see all that's happened with the Aswang raids.
Recon isn't the main point of an attack sub, just a nice bonus.
2. Those small boats can't detect submarines in any way except visually, which is more the domain of aircraft. And the Cannalans don't have a dedicated naval search airplane yet.
They don't have hydrophones yet, and in any case their helicopters don't have the fuel endurance to search effectively.
Getting them to waste a design is in fact the whole point of Das Boot.
3. Again, it takes a turn for them to make depth charges, during which we run rampant and make the missile sub next turn.
Could be solved by focusing on crash-diving capability, or a snorkel.
Anyway, a sub design proposal (totally not based off the Type VII U-boat):
UFN-SS-45 Archer IIThe Archer II is a vessel that builds on the tradition of the old Archer Destroyers, albeit by sinking intentionally. It's Forenia's first proper submarine, using a strengthened pressure hull to sail safely beneath the waves, with bow planes and stern rudder to steer. The Archer II has dual diesel-electric propulsion depending on whether it's surfaced or submerged, based off the diesel-electric engines in the Vodka. Armed with a load of up to 14 torpedoes fired from 3 bow and 1 stern torpedo tubes, its intended role is to sneak up and put torpedoes into Cannalan ships. The torpedo rooms are designed with some extra space, should we later develop larger torpedoes. On deck, its conning tower features a periscope for stealthy observation, as well as an extensible radar mast for long-range detection. Short-range however, it relies on an active sonar in the bow to seek out and target enemies, developed from the passive sonar of the Whalesong mine. It doesn't have any other on-deck weapons, forgoing these in favor of a more streamlined design for speed. Instead, emphasis is made to improve its crash-diving speed should the Archer II come under aerial attack. If there is time, a snorkel to allow the Archer II to recharge its batteries when submerged at slow speed.
UFAF-SNB-45 'Tubby Duckling' (1) : Madman
Microprocessors (1) : RAM
Ekaterina (3) : Andrea, Kot, NAV
UFN-SS-45 Archer II (1) : Cnidaros
The whole point of Plan Das Boot is that we pull ahead in action economy, since the Cannalans will have to make something against a torpedo sub, which will be ineffective against a missile sub. Plus, getting Naval Advantage next turn for landing on the Plains island.
In case people don't want a sub, though, my second choice would be the Ekaterina. I believe introducing new elements is going to be more effective in getting back Naval Advantage.
PS. Sell the Uranium to the Soviets for ore. They've got spies in the Manhattan project, they definitely know how important uranium is about to become.
Also it just occurred to me that if we nuke the Cannalans/they nuke us, we could end up starting WWIII less than a year after WWII ends. What fun!
Hey...if we could do this, why not sell both Uranium for an Ore and Oil boost? You know, achieve the objective of diversifying the fronts through the massive boost that would provide?
I thought of that, but it seems too OP to have Uranium be worth both Ore and Oil together.