In case Turkey decided to be annoying, that's an expensive asset to bottle up.

As part of NATO, it would be party to the agreement. And after allowing transit of the Bosporous into the Black Sea, it couldn’t very well deny transit out.

Plus why let the Russians know to that degree of geographical certainty where a sub was?

The Black Sea, though contained, is still a pretty big body of water (larger than California). And it’s surprisingly deep. And absent a Russian Navy (remember Turkey?) there’s be little worry about surface searches. And that Air Wing? Base part of it in Romania instead of Poland. It could cover the western half of the Black Sea and prevent Russian air searches- through interdiction and/or jamming.

Park the sub somewhere between Odesa Ukraine and northern coast of Turkey. In case of Russian attack into Ukraine, its first mission could be disable the Kerch bridge.

I’m generally hesitant to engage in speculating on such scenarios, but assuming there are any competent tactical planners left in the Pentagon, I’m sure they could come up with a vastly superior plan than the one just outlined by the guy sitting in this armchair.

But that might be a big assumption on my part, and I’m not at all sure that any such plan wouldn’t end up on Putin’s desk before it could be implemented.

In so many ways, we’ve royally screwed ourselves.