We'v come across situations where the domain links
point into are rather large. Take as an example a
'milestone' type that links to
'bugs' that are to be closed for this milestone to be
released.
Right now the 'menu' method will display a menu with
multiple selections, which in itself is already not
very ergonomic. If I now select a new bug (and I happen
to forget to press <shift> or <ctrl> (can't even
remember which :/), all previously selected bugs are
unselected.

It would be nice to be able to address one link at a
time, both, for selecting as well as unselecting.
Here is how I imagine a good UI for a 'milestone' form:

* display all currently selected bugs, with a little
'remove' checkbox
  appended

* display a single-select menu at the bottom, labeled
'add this bug'.

I'm wondering how much work it would be to make such a
feature work
with roundup. It appears the set of display methods
('plain', 'link', 'menu', etc.) would need to be
augmented by one.
I hope others will find such an interface useful, too...