Something like a Hand Cannone could be fun. Very primitive, handheld cannon. Heavy and clumsy, innacurate…but powerful. It could be given bonus damage against objectives like the doors of Citadel, or other seige weapons. Maybe do partial damage to things like the Palisade wall of the same map, that normally needs ballistae to damage.
Balance out the possible objective cheesing by limiting the ammunition heavily, and making the weapon reload painfully slowly. Might encourage more melee archers.
Very much like the idea of a Cannoneer sort of spin to Archers. However it would be one of the more difficult weapons to balance. How a player behaves when shooting at enemies that are in close proximity of team mates is what makes me all the more curious though!
Making them cumbersome enough to encourage more liberal use of a secondary weapon like the shortsword tree could be a decent way to go, especially if we include misfires and a prohibitively slow reloading rate. Having to brace to fire the cannon would also help encourage people to cover a canoneer, since they can’t retreat or easily/effectively defend themselves if they were attacked.
Really try and encourage it’s use against static and large targets, rather than other players. I guess, maybe, a hail of grape or chain shot for FFA or team deathmatch, but trying to mainly focus it around destroying objectives in TO games.
Even in maps without destroyable objectives like the second phase of battlefield, where it could be used against the ballista or catapult, or the agathian castle to damage/destroy the burning pitch pots above the gate.