I like the idea of poise being implemented, and I think some minor changes need to be made, but I feel it will be detrimental to certain aspects of the game if it is not done with care.
Maybe if the knight could take a single arrow and continue the attack, or that an archer or MAA with no shield can be more easily staggered (possibly even post-swing) would be great, but I can see knights becoming too OP if a full blown poise system was created. A possible compromise in this situation would be to make the knights slower to compensate for their high poise, but then again I think knights are slow enough as it is.
I think that it works so well in dark souls because it is a single player game that relies on stat building and equipment management.
EDIT: Reading over your points again, I think that what you’re suggesting is a bigger change than you realize, and IMO I think the game is quite balanced already. And while everything you said made sense, it seems a bit too overboard in relation to the minor problems people are experiencing with classes, and could possibly even affect combat strategy altogether.