I would be interested in a method for creating SubTask Issues. Attempting to use createIssue fails saying invalid issue type. Sub-Tasks need to have 'parent' issue. A method could be just like createIssue except you would have to specify a parent issue key to setup a hierarchy. Something like this would be useful
createSubTask( token, Parent_issueKey, newSubTask )
(which could return a remoteIssue like createIssue does) It would have to check that the Parent_issueKey is not a sub-Task already (I don't think sub-sub-tasks is allowed). This method would be a useful feature.