Obviously you don't need tanks or B-17s for occupation duty... were plans being made to use them against Japan prior to Hiroshima?
Yes. For example, from the plans for operation Downfall, we see many of the formations that was preparing for the assault on Japan were deployed in Europe.
For example, 20th armored division was slated for the assault in Tokyo, but due to the surrender of Japan, was never actually sent to Asia.