Many thanks for the feedback, and we are very happy to hear that you are liking the game. We will probably make a separate forum for posting new ideas and commenting on old features going forward, but currently it is ok to post all such topics here.
We have indeed thought about the crafting aspects in the game, and nuggets of ore have been part of that thought process as you rightly point out. However, any such system has to be well-planned so that it actually adds enough to the game, rather than making the game experience more laborious (if you actually have to use it to improve your odds of success in the game), or just being a curiosity that nobody uses (if not very useful).
So, the answer is that we have not yet come up with a crafting system that would add a sufficient amount to the gaming experience. Such a system can probably be devised with more planning, but so far we have decided to concentrate on other features that are more straightforward to implement and that have more obvious benefits for the gaming experience. And there are a lots of them! But maybe the crafting system's time will come, too, but currently it is not on the top of our new features list.
Regarding poisoning, we just made (for the forthcoming 4.0.21 release) a fountain of poison and a potion of poison for poisoning weapons. And now all sharp weapons, not just bolts, can be poisoned. Potion of sickness actually makes you now (deathly) sick, rather than being poison (logical, right?). Maybe corpses could do something on that front, too, but maybe we have to think it more from the sickness than poisoning angle. That said, all sicknesses in NetHack seem to be deadly. Maybe the whole sickness / poisoning system needs a bit more attention to allow for interesting new mechanics. Although not every corpse needs to spread deadly sicknesses, I think. This is an example of a feature that is much more straightforward to implement and make meaningful from a game experience standpoint than a crafting system, which in turn requires a massive amount of planning, design, and redesign to make it work in a useful way.