Fightingsteel - you have similar views to me.... a few answers for you;
Sadly destroyers still treat you as a sub .... no way around that I'm affraid. As far as I Know changin this requires modification of the .ACT files and I'm not aware anyone has technically managed that, ever.
For convoy escort career ... I believe it is possible to give commands to ships, but have not investigated how to configure this yet... but it is deffinatley a feature I planned to use ... makes an escort career so much more meaningful.
As for the capital ship engagments, I agree, but was thinking that a little more German raider traffic could be configured than historically accurate (more trips out to sea by Scharnhorst, hipper, Scheer etc.) and then a career of raider interdiction. Career could be structured to pick up on many of the "potential" aval actions ... including stuff like Norway invastion, Russian convoy covering, Channel Dash, search for Bismark etc.
What I was thinking is we know certain events happenned and there were certain allied reponses and the resulting battles or non events where the fleets missed each other .... but I figured if the player was controlling a ship and it resulted in something else happening ... then so what ?
After all, when playing as a U Boat captain, it is possible to change history ... In SH3 GWX I lost count of how many times I sunk ships from Force H as they rushed to find the Bismark.
So I figure it should be possible to configure several careers commanding different classes of ships, with some comlpetely non historical missions thrown in for a bit of fun.
And have not given any thought to Pacific career right now ... will come later I suspect...... after all..... Japan & US were late into the war
