It shouldn't be about micromanaging. There is no limit to what one could add to make the production line to produce effective weapons even longer. Question is, where will we set the limit? For bows and arrows, one could need a bowstring, special wood, arrowheads, rope and appropiate tools plus the facilities to produce such a bow which again needs an array of different materials.
I think the limit needs to be put rather low because in scenarios where you need weapons and where you need to produce the weapons by yourself (mostly settlement melees), you need them fast. It may not be tenacious to produce (at least) the basic weapons, and, most importantly, having to produce materials that are to be consumed by your warmachines like the cannon (or e.g. your train, blimp,...) is like the concept that clonks have hunger, can get tired or freeze. It is tedious and not fun.

So, on a general note, I plead to require as few materials that are consumed constantly (by weapons) as possible. Just because of this, the coal plant was practically never used in Clonk before and the catapult was almost always favoured over the cannon (if several gunpowders were not just placed in every cannon by script). And that's why ~every munition is bought and produced in packs (Arrow pack, lead shots,...). Consuming weapons mean that you need to keep your economy running all the time which you don't want and can't if you are inmidst battle (unlike in e.g. The Settlers, where it all works automatically).

Looking back on the cannon as we know it since Clonk3, it just has been too tedious to use it to be of value in a fast-paced melee as we want to have it in OC.