Thanks, Gavin. Leaflet core does not support rotation, but the recent leaflet plugin that I mentioned looks promising; it was published 5 months ago (the Leaflet repository entry you linked to ended in 2018), so I'm hopeful that it will work with some of our current formats. We already have long usage with leaflet and users with various data formats, not just Esri formats, so switching or adding renderers is a big investment.