Thanks for adding the option to seperate users and accounts. I think this is a good first step needed in order to improve WHMCS and make it more suitable for accounts that belongs to corporates / companies instead of individuals.
In general these are the things that are not handled by the current way it's working in WHMCS - even after version 8:
1. When a user log in to the account - he see all the tickets from all the other employees of the company / all the other users connected to this account. There should be a way to show each user only his tickets and allow the account owner to see tickets from all the users connected to this account.
2. Information management - The same as above, user should be able to change only his information and not to see or be able to change other contacts / users information. the account owner is the only one that can see and edit everyone.