Hey Utku,
Please don't discount the quality issue so easily. It isn't just about bandwidth, but also delay. Some of the RD protocols can add to the delay due to all the encryption. If they run over TCP, that adds to the overhead as well. You will probably have some kind of load-balancer between the clients and the servers, another step and more delay. Will this be a problem? I have no way to tell you, but please remember that you may end up putting a lot of work in and then find that the audio issues that you come across cannot be solved with bandwidth alone.
Moving on to the main part of your question.
I am not sure how much you know about IC's use of stations in general, and the SoftPhone in particular? The Softphone makes use of Managed IP Phones, which relies at least some extent on the end-point in question being the only one present on the host. With a client desktop installed SoftPhone, or a hardware phone, this is a given. This means that the Hostname, FQDN, IP Address and MAC address can all be used to uniquely identify the endpoint. This is not the case in a T/S type environment.
When you deploy the softphone, you configure the Managed IP Phone object in IA. Hardware phones are ultimately defined by their MAC, SoftPhones by their FQDN. As far as I am aware, there isn't a way with the provided SoftPhone to override this and provide SIP registration details directly. The problem here isn't getting it to work - it's getting it to work multiple times on the same machine. Now, there may well be command-line options to get around this, but if they do exist, I couldn't find any information on them.
One option might be to use a 3rd-party SoftPhone (IC would just see it as an Unmanaged Station).
Sorry I cannot help any more than this - hopefully another member of the Community will be able to offer a better solution. Alternatively, I suggest you reach out to the Genesys Professional Services organization - they often have creative solutions to problems like this.