This isn't really UMLising as it would be an optional feature - that is, by default it would not be on.
In ArchiMate, directionality is important (but not often mentioned). However, in the specific case of Access (an implied Association ) it is even mentioned in the standard. In a live model, you can always hover over a line to see the direction, however, when you print or take a copy and paste, you can't! In those cases, where there might be some doubt as to the directionality, I'd like to be able to indicate expressly.
In any event, on our modelling environment, we'll be indicating directionality, where it's not obvious (or not implicit) - as we use it as important metadata about the semantics of the relationship. I'm just hoping I'd be able to hook into a standard mechanism rather than "roll my own".
Paolo