Nothing against it in principle, in fact I'd expected it to be possible when I first bought the toolcrafting skill several years ago.
One caveat though: with limited development resources, how high a priority should this have given that the cost of craft tools is so low there's really no point in crafting your own unless they add some bonus to the basic tool (as do op tools, obviously).
So a crafted tool might need some bonus capabilities. Not big ones, like armillo or rubarn, but maybe a few percent boost in craft success rate? This would entice crafters to make their tools, thus making the whole thing worthwhile and not something that people may try once only to never use it again because it's just so much faster to buy the tools.
One caveat though: with limited development resources, how high a priority should this have given that the cost of craft tools is so low there's really no point in crafting your own unless they add some bonus to the basic tool (as do op tools, obviously).
So a crafted tool might need some bonus capabilities. Not big ones, like armillo or rubarn, but maybe a few percent boost in craft success rate? This would entice crafters to make their tools, thus making the whole thing worthwhile and not something that people may try once only to never use it again because it's just so much faster to buy the tools.