Players use fewer ships and they generally know what they want from any given one and when, thus manufacturing them on demand is fine. However, with weapons the matter is muddier, since every ship can use a wide variety of them and if you want to retool your fleet, you have to think ahead and order all weapons you will need, which is going to be inconvenient, if you don't even have decided on loadout of the ship you're also ordering or just bought on some market. It would be nice if there was a stockpile of weapons you have blueprints of in all your colonies (or all your colonies with Patrol HQs or something) so that you don't have to worry if you have some particular bit already there and don't have to wait if it's missing. It would make endless hoarding somewhat less important as well (since weapon availability, while better than before, is still not good enough to fit the ship with a workable loadout without visiting several other markets).