A hardfork does not require 17/20 in a strict sense: Yes, it is a custom to enact them at that point, and generally respected as a means to avoid a blockchain split. However it is possible to hard fork that meta-rule itself, at any support level.
That would likely result in a split, no matter what subchain is longer, but only one of the sides owns the branding, has the exchange listings, and has the capacity to support core development.
Thanks for your sharing your thoughts. I really didn't know much about the hardfork procedures.
In the above case, Sun's chain will likely emerge the ideal chain. Cheers!