well, i admit i'm horrible at creating balanced stuff at the first try, but i thought it like that:
in the early game, it allows you to have a reasonable quantity of reasonable quality weapons by the first autumn (or even the first summer if you want to go for the cheapest variant) without needing to set up a metal industry (you can even embark without a pick, not dig a single block and you'll be fine and well armed for a good amount of time if you chose your embark items carefully). just kill and butcher some animals and turn their skin, meat and life force into axes with eyeballs
in the mid game, with all the dwarfite (they are evil, after all) and the caravans running around, it won't be very useful, unless you don't have access to good metals or fuel, in which case you can emphasize in your meat industry and arm yourself with pretty good equipment without using a single forge.
in the late game you'll probably have access to top tier metals. you'll also have access to a lot of resources, however, and that means that you'll be able to produce weapons from the best quality material (slightly better than steel but takes a lot of resources) automatically in masterwork quality.
so the primary purpose of these weapons is to make metal entirely optional for the wasps. at least that's how i thought it, suggestions are always welcome and your idea about them having automatic syndromes is good. i should really learn more about using itemsyndrome...
also note that what i wrote in my first post, about the time it takes for them to grow, is entirely debatable. on retrospective, it seems that i'll make the worst grade only grow in less than a month and the best in a year maximum.