I'd definitely like this. I'll go one further and ask for a one-click temporary waypoint system, for when you know you need to head to x spot but don't want to go through the journal to check quest, or maybe it's something not quest related. I'm thinking of the type you see in a lot of GTA style games that goes away when you actually arrive there, but helps you maintain your bearings in the meantime.

I want to stress this would be in addition to a permanent marker system though.