I'm not really against a HF that has widespread support and after extensive reading I honestly think this proposal would be pretty safe. And I don't mean this as an "appease the other side" option either. I actually just think this is a good idea and HFs only worry me in a contentious environment, if it can gain wide support then I'm on board.
This proposal suggests nothing that assumes unlimited resource availability, or that a hard fork is not a risk. In the meantime we would have another year+ to activate SegWit and implement many other scaling solutions as well as allowing technology/bandwidth/resource costs to continue to decline before implementation. It would give everyone ample time for preparation, and if 95% wasn't achieved, then business as usual and we have far less to worry about when it comes to some terribly incentivized system like BU.
Summary: I prefer Soft forks as the more conservative option, but I don't see any significant downside to a long-term scheduled hard fork that doesn't drastically shift Bitcoin game theory into ridiculously untested waters like BU.