At initial contract signing I pick three bases, correct?
I could however be assigned anywhere!!!
Could I wait for my choices to come up?
If I am at my desired base and upgrade is available elsewhere, do I have to take it?
Can I bid to upgrade in particular domiciles only?
It all seems quite random, like you said. Anything is negotiable if they need you.
I have heard of a direct entry captain, who negotiated into his contract a clause that he would ONLY be assigned "Mediterranean" bases!
(France, Italy, Spain or Greece potentially)
Or he is out...

They are sometimes willing to jump over hoops for high time, current, NG captains.
Ohhh the power of leverage...
Thank you very much for your reply.