All that said, I don't think updating THF's knife is the answer. It won't change anything.
Replacing it with an accessory is a fine start, but for the system to be TRULY designed not to gimp THF's already pretty crappy dagger damage, it would have to allow offhand hits to raise treasure hunter level.
If not, we're still going to be forced to single wield a dagger in any case we want to raise treasure hunter to a higher level.
