That's an interesting idea Bryce, do you think riders would take notice of such a "rule"?
I'd put a yield sign on the climbing trail just because the default rule is that climbers have right of way. But in this case the piece of trail at the intersection was originally built as part of a DH trail and the intended use should be respected. Plus its fun to carry momentum through there.
*edit - mudhoney already mentioned a 'stop' sign might go in here