Proposal: Call the Gatling Cannon the Rotary Cannon. Also, a very nice design and - it being a support weapon - we're fulfilling all of our needs.
Now, what should we revise? As I had already said, I can see three (four) ways to go:
a) Add a single "Breech" cannon to our armed vessels. This is a stopgap measurement, significantly increasing range and firepower of our ships. They still remain the same, though. This is useful since I'm guessing the enemy will do something naval-focused this turn, and we only managed to gain an advantage due to shore-based artillery (imagine them ship-mounted!)
b) Add a bayonet to our rifle. This would give our soldiers a melee advantage, and the ability to repel horse charges by shifting to a square formation. This is useful since it increases our soldiers' ability across the board, and is the safe revision.
c) Revise our cannon ammunition. This would add both a shell, canister round and shrapnel shell. This is useful since it increases the capability of our cannon, giving us another way to avoid massed charges. They also increase our bombardment ability.
d) Revise our shovels. Introduce digging courses and standardized shovels for our soldiers. This is useful since it allows them to use fortifications, making them less vulnerable both to rockets and charges.
Of course, the question is whether d) counts as a revision.
For myself, I'm in favour of c, d, b and a in that order.