From a gameplay perspective you could lock the front turret, use it as a primary, then give the ship a really high autoaim FOV and pretend that's the turret moving.
Though the problem with that is that it would look terrible in 3rd person as the turret wouldn't actually move.
The other solution is to just use a capship script to allow the player to set targets and priorities for all the turrets.
The last option is to just say "**** it, no primaries", the player can probably deal with that since heavy bomber primaries are basically only there to mount maxims for better disabling and a bit of extra damage vs capships. You don't lose anything super important by removing them entirely.
Build "launcher" models for the weird looking torps - I'm 99% sure that this can be made tow rok with the engine.
This is basically what BP does with its external weapon models, so yes, the engine does support it.