Would it be possible to revise a correction to the faulty system in the base model while also retro-fitting an alternate version? We could try to make a combat-drop version with a couple of turrets from our bomber and some internal accoutrements for dropping, such as rails to slide cargo along and rings/bars for crew and paratroops to secure themselves to when they don't want to fall out...
Subs aren't going to be that helpful since they already have defense a against them and two world ears have proven that focusing on subs doesn't win the naval war.
I would say that World War II made a pretty good argument for submarines. The problems seem to have mostly been communication-based but all sides still used them quite effectively. And defences are good, but the main issue of a submarine is finding it in the first place. You can't just scour the whole sea in hopes of spotting them. Sure, it'll happen but most of them will doe their thing, occasionally pop up for some air and a look around, then pop down again with nobody any the wiser. They CAN block ports and straights, but there don't seem to be many straights and if we can't secure a port than we have more pressing issues, assuming that they even need a port(which is a fair assumption given current expertise)
I'm trying to emphasize what we really need out of this thing. Namely, plentiful-ness.
Actually, I think it'd be fine at Expensive.
Given that our transport ship is only 1 TC, I find it difficult to imagine that capacity will get us 2 TC. I only see 2 TC by air happening from a combination of 'enough' capacity combined with massive quantities.