I absolutely love this idea. I believe that a connection with one's weapon would make for a very interesting aspect toward play. As far as your cons go, marginalization of weapon crafters might not be so bad if your idea about breaking down some other weapon first required you acquire said weapon. And maybe the benefits of sacrificing said other weapon are small enough to give you the option to do so multiple times.

Also, I really don't see how the idea would be completely closed off to DoL and DoH classes. Instead of using your tool to kill, use it to create or gather. I'm sure the idea could work for them, too. Not often do I find an idea that I totally flip over. You deserve a cookie (and a serious consideration from the devs).