@ahargreaves_FW, we don't have any plans at this time to support Incident submissions, but I will certainly log this issue in our backlog as something to consider when we do an update of the Road Closures solution. Reading through the Waze spec, it seems incidents are still reported as polylines. From this it seems like you just need to add these additional values to the type field domain and specify the appropriate type when you draw the closure line in the Road Closures app:
ACCIDENT, CONSTRUCTION, HAZARD, POLICE, CHIT_CHAT, JAM