In any case, I don't think having the author rewards pool returned to the proposals pool in a way that bypasses witness consensus is in the spirit of how Hive is designed

There is nothing in the "spirit of how Hive is designed" (or Steem before) that is contradictory with posts being voted to support development work, marketing, promotions, platform resources, or other such efforts. The original Steem white paper discusses "subjective proof of work" where stakeholders vote to allocate funding to "work", the determination of the value of which is entirely subjective, including examples of supporting charities or political agendas. It was never and was never intended to be only about content.

Prior to the DHF, voting individual post payouts was the only way of funding such efforts. The DHF adds another mechanism to handle these sorts of things (with a significant benefit being that it is easier to define a specific budget and payment schedule for a project, as opposed to the rather erratic way that post payouts do, both of which were recognized as major logistical obstacles with funding larger or longer term efforts through posts), but that doesn't mean there is anything wrong with using the original method to fund these things, including by sending that through the DHF (and thereby gaining access to the budgeting and payment scheduling system).