Thanks for the replies! :)
Anyway, I just finished the steering behaviors the other day, and the ships are now chasing each other all over the screen. I went with the simple solution, which is to apply the desired vector as a force somewhere near the ship's nose, increase angular damping to about 0.8, and multiply the angular rotation by 0.95 when the heading of the desired vector is less than 30 degrees. Its an ugly hack, but it gives good results. I'm going to simulate thrusters firing with data retrieved from b2Body::GetLinearVelocityFromLocalPoint.
In the works - using Lua as a scripting language for RML (Rocket Markup Language, an HTML/CSS-like language for the GUI), should be simple enough, but there's much work to be done refactoring the mess inside ShipEditor. When it's done, I can then use Lua inside RML element event handlers, like:<button id="myButton" onclick="Gui.Document('MainMenu'):GetElementByID('myButton'):SetInnerRML('You clicked me')">Click</button>