Advanced Topic, be warned.
First, i would suggest making it a subclass of the redeemer shell, and making its launcher a subclass of the redeemer itself.
Then:
- Chainguns. make your launcher weapon do all the firing when the pilot presses the 'fire' button. however, instead of running a trace (the best chaingun trace examples are of the minigun, complete with spiffy little lines of light) from the weapon like usual, simply imput the projectiles location and rotation instead. This way, the weapon fires the bullets, but as far as the weapon is concerned these bullets are coming out from the location and dirrection of your aircraft.
Though possibly to make another weapon for the chaingun state, i would recomend you leave this alone, as modelless weapon timing is a general pain in the rear, and it is a frightfulyl compelx system to amke a weapon that temporarily blocks out other weapons, esspecially while flying around this modified redeemer rocket. Though this is the best solution if the player rides inside the aircraft (aka a strangelove clone to some degree) it is probally the worst choice if the player stays stationary like with the basic redeemer weapon.
- Collsion. well, the hit something - explode is pretty much made. You may want to play around with the actual explosion setup itself, but the general hitwall is perfect i would imagine. However, there should be a function along the lines of processtouch or the like. in it you want to test if the actor it touched is a pawn, then you want to give that pawn a blurp of acceleration in the dirrection the aircraft is moving, or something similar. All in all, i think there is a lot you can do here, and it would take a lot of playtesting to perfect.
- Hover. This is the hard part. The easiest, though far from 'best', way to do this would be to add a throttle system. Basically you will need to take a look at how the rocket moves foreward, and add a fucntion (preferably keybinding started) that increases or decreases things ability to move foreward. If you are creative with it, you could havea brake button that would slow you to a hover if held down, and will slowly speed up if released. I would warn you about rewriting any of the mahor movement issues of the weapon, mostly becase the netcode is heavy and it is generally complex; leaving it alone iwll leave you with more than half decent air physics, and in theory basic netsupport (at least for the projectile) for the inevitable time when you try to play this onliine with your friends