How can we improve WHMCS?

There are currently hooks for when a user account is created/deleted. However, it would be nice to have the ability to run code when a user (such as an existing user in the system) is added to a clients account.

Since a client account can have multiple users it makes sense for this to be included in the base functionality. An example scenario of how this would be useful, is a custom module we have that syncs all users and clients to intercom for customer support request. When a user is added to an account, then we need to know so we can add that user to the clients account in intercom as well. Same goes for when a user is removed from a client account, as we'd then need to update our system in intercom as well.

Not having this feature requires us to have a sync process based on a daily cron.. which isn't preferred. We'd rather update the system on a per-event basis and avoid using a custom script ran via cron.