you can still shoot while in mouselook in vanilla. But the weapon projectile direction is not reliant on the direction of the camera for vanilla vehicles. For our blasters it is. That's why the blaster goes where you're looking.
The basic reason for this setup is so that the blaster bolts from the fighters converges then goes straight forward from the craft, helping with the aim. Previously when we had the xwings (for example) firing straight from the wings then:
a) straight on you would actually miss with most of the shots or even have it where the enemy fighter would be dead centre in your targetter and the shots would go around it
b) when we angled in the blasters in slightly to converge you'd have them converge only at a fixed point ahead. If the enemy was not at that fixed point (if he was too close or too far) then you'd have the problem listed in a.
As such, we eventually were forced to set the actual projectiles to fire straight from the nose so they line up perfectly with the crosshairs at any distance. The shots you see coming from the various wings/blasters on the spacecraft are tracer rounds which converge with the real rounds around 1000-2000 metres away. Without this accuracy becomes so low as to be almost impossible for some of our fighters to hit the enemy for the reasons listed above.
There are other reasons as well. Like I said, blasters are not like vanilla weapons. You can't see most vanilla weapon fire so they don't have to wire it straight up to the nose of the craft. Plus all the vanilla maps (bf2 or 2142) are only 1-2km long maximum with an engagement range of a few hundred metres. On our spacemaps each side is 8km long and you begin engaging at the enemy at 3km away. The scale is rediculously big compared to what the engine was originally designed for.
Fear the Woodzilla
