Those are some very useful suggestions, Sir Charles! Only gave keyboard steering a serious try two days ago, and it's a great concept that just needs a little bit more love to shine (particularly for bigger, less maneuverable ships where it is really useful, IMHO). So basically +1 to all your points. :)
Two more things I would like to see:
1. Add an option to toggle fixed camera facing (as opposed to being linked to the ship itself). Pretty much what a gyroscopically stabilized tank turrets does. This would make aiming and keeping track of more distant targets while maneuvering easier.
2. Add some visual cues to make aiming in this mode a little easier. In mouse steering mode you are more or less always aiming towards the center of the screen - where the ship's front is pointing. For most ship designs that are longer than they are wide or tall, this means the forward-facing weapons will be aligned more closely. In KB steering mode it feels unnatural to have the mouse cursor show up, and aiming to the sides can be problematic when the guns are spread out wide between bow and stern of the ship; hence I propose adding optional visual targetting indicators (lines) drawn from each turret towards its target as well as changing the mouse cursor to a targetting reticle in this mode (unless the key bound for mouse interaction is pressed).