It is also worth noting that the game provides 10 hit cards for the invader's barrage siege machines. That's enough components for 5 barrage weapons.
If they only wanted us to use 4 barrage weapons with not only provide 8 hit cards. Everything else in the game (excluding hour glasses) is naturally limited by the amount of components in the game.
Might one of the veterans or designers shed light in the matter?
There is an extra marksman too (if i remember correctly)