Watching an issue as a non-user

We are in the process of deploying JIRA for support (support.rivermine.com). Our customers have a request for us, that we cannot accomodate with the current system. They would like to be able to add others at their organization to watch an issue once they open it. This can be accomodated by going into "Watching" but there are two major problems.

1. Since multiple customers are on the system, we have to restrict permissions to the user browser so that customers cannot see other customers names, email addresses, etc. This means that to add users to watch an issue, a customer has to know the user's ID on the JIRA instance. This could be resolved perhaps by a rule that we could configure such that users can use the user browser, but will only see users at their organization. Note that we currently have a workaround that classifies users at an organization based on the email domain.

2. Related to #1, this workaround requires that customers have a JiRA login. This is not the case for all users. Most often, our users serve as a central contact point for our customer's organization, and other users report issues to those central contact points, who then open tickets with us. Ideal would be to allow either JiRA users or just any email address to be added to the watchers list.