I believe a generalized exception for cases where an RC or champ determines a type upgrade is necessary for proper routing is sufficient, but I’m willing to get into it with making the list more specific. I do agree that a specific process is warranted.
I don’t think I can think of any situation where a user might upgrade a road type without approval. I imagine any user experienced enough with road types to make the determination that a higher type is “necessary for proper routing” will be familiar enough with their area’s champs/RC anyway that contacting them will be a non-issue; and further, the champ or RC may grant more latitude to certain experienced editors in making this judgment within a particular area or region.
I don’t envision that champs/RCs will have too hard a time understanding why other champs/RCs have made these determinations. Perhaps oversight via posting all such determinations to a state’s Wiki or forum will be sufficient.