The next thing to consider is what has priority, the continued unabated rush to get new functions in, or is it wise to stop including such functionality until some of the projects that /are /prioritised by the WMF become a reality.
But a significant number of features are written by people who are volunteers. Try telling volunteers that "the WMF has not prioritized that feature", and see what happens!
If this means that Brion does not do anything but SUL for a month on new functionality until SUL gets done, it would be in your interest to help him in order to get your stuff in production.
If you want SUL done, and you take a "means-justify-the-ends" approach, then the best approach is probably to kidnap him, fly him to Antarctica, with a laptop, various test boxen, a supply of tea, and dump him by himself in an isolated hut with adequate power & food, but no internet connection whatsoever, and no phones, no post (i.e. no way of communicating with the outside world) and no other responsibilities _whatsoever_ besides doing SUL, and don't release him until it's done.
Failing that, stop asking so few people to do so much stuff, and then acting surprised when the non-urgent items get pushed back. For me, the remarkable thing is not that SUL isn't done, but rather that anything has been done about SUL at *all*.
All the best, Nick.