Manually changing user rights for 3CXSkypeGateway accounts is on your own, and, subsequently, on your own risk, we don't take any responsability for such changes.
I repeat what I already said several times: these accounts are required only to allow multiple Skype client instances to run at the same time. Nothing more. Due to security reasons, these accounts are highly recommended to have MINIMUM privileges, exactly as much as is needed for the Skype client to run.
Then - if you have a physical, hardware gateway, it does run in its own box, being connected by network to the PBX, it doesn't require user accounts privileges handling. Therefore, since 3CXSkypeGateway has been designed in the same way ("set it and forget it"), there is no practical reason to force its installation on a machine not suitable, particulary a DC. If there is a DC machine, then there are also client machines, so 3CXSkypeGateway can, and is recommended, to be installed on such one and connected, as in the case of a hardware gateway, by network to the PBX.
If you look carefully on questions related to 3CXSkypeGateway, you will be surprised to see that more than half are related to user accounts handling. If 3CXSkypeGateway would allow domain accouunts, then perhaps 90% of our technical support will be focused on debugging an maintaining computer policies instead of gateway specific issues.