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
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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.