Crafting is already limited as it is because it can't produce level 6 items, so the issue here mostly regards the early game. The parts required for tools and weapons items are most reliably aquired by scrapping lower level versions, so even if you just crafted a level 3 machine gun, that level 2 is still useful as material for further crafting.
You might find this post my Madmole interesting if you haven't read it already. Also some more here.