I'm looking an email hosting environment that wants to expand to also offer RDS to the existing email customers. There is an existing AD environment already. Each customer already has their own UPN domain that distinguishes them from each other customer. Theoretically, each customer would have their own segmented subnet that would contain an RD Session Host and file/application server that is managed by a central set of redundant RD Gateway and Connection Broker servers. Group policies for things like folder redirection and computer lock down policies would have to work. Of course no access from the individual customer subnets directly to the existing AD domain servers with all the user accounts would be wanted. I can not decide if making a subdomain of the existing user accounts domain and joining customer servers to the subdomain or setting up a resource and authentication forest set up would be best.
Any input would be greatly appreciated.