THere are no options for upgrading on Delta UNLESS you spent a lot of money on the ticket and get lucky.
As a FF I have reserved the bulkhead seats so I know that they aren't currently all "held" for airport release.
(Of course the "it's fine" to move someone if they need the seat for medical reasons will ONLY apply if it's not YOU that's moved....

Honestly, on this board that would grounds for a class action lawsuit by some posters

)