I've always been curious about what could be done with wing commander 3/4's engines since there seems to be quite a lot of overlap in the code of both games. I don't know if adding entire cockpits would be possible but I guess you'd start with the longbow/hellcat 5 and go from there.
That was my first impression, too.
But then I tried it again, and also WC3 without cockpits, and then later other games (like X3), and I got used to it.
Now I see the advantages: I have a better view.
Of course I still like cockpits, especially like in WC1 with exploding instruments when you are damaged, and damaged screens. And I remember that sitting in a raptor had me always FEEL that I was in a heavy fighter. I liked that.
Ok, but some cockpits were IMHO really too much, Privateer's Tarsus, for example.
So I think it is really a matter of taste.
I also remembered that some people didn't like the Prophecy cockpits. I kinda liked them. They didn't block my view, but I still hat the impression of sitting in a cockpit.
But many people would prefer flying without cockpits. There was a discussion in a forum (about the X series, in that case X3) that brought up interesting points about that. A mod brought back the cockpits from X2 in X3 and there were really some people that wrote "What? I was happy that they finally got rid of them!"
And then, of course, it is also something you have to develop. It is much easier to just move the camera from above and behind the ship to right in front the ship. Taddaa, cockpit view. Modeling cockpits would take time and money, especially since many people wouldn't like 2D-cockpits. That could be another reason why there are no cockpits in many games.
(I don't know about WC4, but I can imagine that the game was expensive enough, so they didn't have the money for cockpits.)
It's logical to have a HUD in your helmet rather then a dense cockpit, even in this day(I would not be surprised if the next generation of fighter jets and choppers use a helmet+cam system as well, with the normal visual for a backup in case the electronics fail.
I used to catch myself trying to peek around in front of the screen in DOOM, that is immersion from the games side.. just like pulling back on the stick as hard as possible to try to avoid crashing into a capship, or playing Wii in an intense way. You don't need a cockpit for that. Draw one on paper and stick it over your screen if you really want to try the effect.