In prior versions of Sakhal, the military containers were a nice way to break up the typical gameplay loop, offering an alternative pathway, if you were prepared to do the following;
Take the risk of braving the cold water to swim across or expend time and resources to get a boat operational. But the current implementation of the container key system makes this progression very linear, (as far as I am aware) the only way to get your hands on one of the keys is by visiting the newly implemented boat wreck.

I do like the new boat wreck, and I do believe that one of the key variants should be kept there. I believe they should be split similarly to the following;
Blue = Ship Wreck, as they are currently spawning
Yellow = Mountain military base / Briefcase maybe?
Note: Yellow is the one I'm least sure of, the mountain base / briefcase is already very good / loaded with stuff.
Red = Military peninsula (T4)
Orange = Regular military (Any location, any tier)

As a Further idea, to return some of that spontaneous nature to the containers. a Dynamic event, where a life boat from the ship washes up on the shore of the main island (Using the life boat asset from the ship) I believe this dynamic event should have a chance of spawning any of the key colours, as this would enrich the gameplay / lead to a moment of "Oh I found this! Now I can start thinking about visiting the islands" allowing someone to stumble upon it even as a freshie