Side effect of 'delete issues' permission scheme entry

In the list of permissions 'delete issues' raises some problems: we dont want users to be able to delete an issue, only admins and say project lead, but we want all users to be able to modify or even delete their own comments. This is not possible right now because of the same permission managing 'delete issue' and 'delete comment'. One way out would be to have customizable permissions, but I did not see this feature in the JIRA version we have.