Please support cck role reference

do you refer to rolereference?

it seems pretty similar to userreference & nodereference (if not a total copycat)
nevertheless it deserves throughout testing (which I'm not doing)
to ensure it properly behaves for every possible combination,
i.e. single/multiple values, limited/unlimited values, required/non-required, and all that for each of its widgets

attached patch merely enables it for driven_diff, without any special consideration,
i.e. it just removes the "unsupported field type" constraint and hopes for the best

BTW: I noticed that having a single value, not required, select dropdown widget, doesn't leave an option to select "none"

watch out, it doesn't mean they are the same.
nodereference does allow "None" option when the field is not required,
so there are differences between them
and thus, proper tests are due

@#6
ok, but it hasn't been committed yet
also, it would require further testing (beyond your particular cases, as stated in #3)