Is there a way to get Views Bulk Operation to place field options in the main VBO exposed dropdown
If you check the "Skip confirmation step" box below the "Change the author of content" action, you can remove the confirmation step.

As for making it a one-click change, that would probably require either extending VBO with another module, or somehow invoking ctools modal windows with VBO. I haven't found any success stories with the latter, but there's this: Ctools Modal + Views Bulk Operations? (drupal.org)