Consider End handles
In illustrator we can to adjust start and end point handles in open path, but it have not much sense. What about to consider this handles to adjust shape of the object fill. Not on strait line like usual, but in way like we want. By the way, if we decide to close the path, Ai should make it in that way too.
So, we doesn't need two objects with stroke and shape separately, it will be one object with adjustable end handles.
Alexandre Soubrier commented
I agree. It should be an option, or even better a default setting to check or not in the preferences.