That unfortunately doesn't work currently. On a RWG map, a single trader may create multiple duplicate waypoint markers on your map's list. The game won't allow deletion of the duplicates currently. I know TFP are aware of the issue though.
Not even offer an option - just do it. Or no gear via quest rewards, so crafting is more worth it. Let Rank 6 gear be available through looting high level POIs or something.