Instead of a single attribute, it should be possible to select the relation and then use a text with placeholders to be shown in reference selector dropdown.
We quite often need to display more then a single attribute in a reference selector dropdown and this should not require a custom widget.
agree with this!
Also, when having a dateTime attribute, you'd want to be able to select the datetime format.
This would be possible if the default placeholder/parameters menu could be used!