Yes indeed. The sooner we deprecate v2 the sooner we can stop worrying about malicious HSDirs.
yes, that was indeed the motivation for my email (mostly because I see how much time goes into the constant detection and rejection of these relays - not by me)
And also we will be able to reduce the requirements for becoming an HSDir which will strengthen and make our network more robust.
That said, I think we are unfortunately still far from deprecating v2 onions:
thanks for listing all these relevant ticket IDs, I pasted your email into trac and I made them child tickets of https://trac.torproject.org/projects/tor/ticket/25955
lets try to link all relevant tickets there