It is a common scenario where different corporate cost centres or individuals owning multiple business entities require separate billing per business unit or entity. Currently, multiple Dropbox business accounts cannot be used easily on the same device. I understand this is hard to solve.
The Simple Solution:
In the admin console:
1. Under Groups, when clicking on 'Create group' button, add an additional Group type called 'Billing Group'. Billing Groups should then allow the selection and assignment of members.
2. Under Billing add a 'Billing Profiles' tab to add, remove and view business entity details, payment methods and associated 'Billing Groups' containing assigned members.
These 2 relatively simple interface changes enable an administrator to setup Corporate Groups representing different companies to be billed separately to those associated entities.
I'd be happy to provide more information on a draft specification.