Carronades: yep, some ships are equiped with them.
Drifting: currently only fireships 'drift', once you ignite them.
I liked the idea of firing while moving, also, but it wasn't feasbile for Salvo I. Maybe we'll see it in Salvo II. The battles are intense now when there's a number of ships all mixing it up, but with 'passing' shots, that would really add to the mixture
It would requre more combat commands. You wouldn't want to automacticly fire at a crippled ship you were passing by, if you were meaing to go after one just past it.