Since i read only the first half of page 1,i don't think that the backstab of the dagger should be implemented,just because imagine if a 13 athletics player swoops around the main fight,and basically just kills off the enemies from the behind,i don't think,that would be fair,or imagine a 2 v 1,and one of the 2 players was using a dagger,and the other one would be using,let's say a shield + spamitar, the guy would have no chance,if the dagger dude would be high ath and would be a decent chamberblocker.
About the blocking,on my crossbowman alt i use the long dagger just because it's really fun to chamber,especially with my high athletics,i can easily chamber 2 hits while backpedalling, turn around and run away.