This is something which was possible in jira 3.12. Unfortunately in jira 5.x, we can't add any watcher if he does not have the permission to view the issue.
Why I require this is I want the issue to be restricted by only some users, but if they deem anyone else should also be able to view the issue, they may add the user as a watcher.
This was achieved in jira 3.12 by allowing users to add watchers and having watcher(s) as a security type in issue security.
Is there any way we can circumvent the validation which happens when a watcher is added to an issue in jira 5?