So I asked Camden if a shelter could be installed there. Sadly, it turns out there is a very good reason why the answer is "no". The stop is on a bridge, which means there is insufficient depth to accommodate the electrics and so on for a shelter. In fact, it's the same reason this stretch doesn't have proper paving, but instead an "imprint" surface which mimics the look of paving slabs.
A disappointing response but at least the reason for it is clear.