DropDown Authors?

Hi all, just two quick questions.

(1) Is it possible to create a dropdown list of authors, exactly like dropdown cats?

IF SO:

(2) Is it possible to force the dropdown author list to display User defined Roles by stating it in the query function?

ie:
(i) If you want a dropdown list of Authors, stipulate authors
(ii) If you want a dropdown list of Contributors, stipulate contributors.
(iii) If you want a dropdown list of Subscribers, stipulate subscribers

Your input would be appreciated.