That might be helpful for some, but it might start to clutter up the map pretty quickly. Coordinates could always be on a separate page, plus if its a 1:50 topo you can simply read the coordinate off the map fairly quickly. If you prefer to hand write on your map, you could bring just the topo and we could update it every night with very accurate stuff, or I could send you the updated info in June and you could pen it in then.
I only have one major area of confusion on my maps, although on the river, it is perfectly clear. My GPS marked the start of the port before the falls about 400 meters from where it seems like it should be on the map. I'm looking forward to clearing that stuff up.