Hello. Sorry for the delay in getting back to you.
This is technically “reselling” our services and we don’t have a reseller programme at the moment and so you would have to use the system as you see it for what you want to do.
We have other customers who do what you are suggesting and that’s fine. We would expect the company to go to you for email support in most if not all cases unless you agree something different with us beforehand.
Sub-accounts would be the way for you to manage this, yes. You could be the Main account holder and use that as a Admin account in effect. If you need any further help I suggest you contact us at https://support.runbox.com