which version of remedy are you using?
If the server outside the SG would be within SG with other two servers then you can control the admin operations better by as correctly said using server group ranking form. can you please tell us the reason behind separating the server from SG ?
escalations can be turned off using the ar system administration console -> server information -> configuration tab. Please refer to the ARS configuration guide which has special a section for configuring servers in server group / configuring servers to share same db without using SG / distributing operations between the servers in such a environment.