I don't think you understood my comment.
I'm not talking about self-signed certificates. I'm talking about CA-signed certificates. Only you create the CA.
Your SOAP package almost certainly has a list of acceptable CAs. Otherwise, you could never add or revoke a CA, ever. That would be pretty impractical, so I have to assume that there is a list.
Create a CA. Add the CA to the list in your software.
This goes on ALL of your devices - no need to customize this for each device.
Now, create a certificate for each server, and sign it with your own CA.
The device will connect to any server signed by your CA.
For added security and control, DELETE the CAs for the public CAs (Verisign, etc.)
Now the devices will ONLY connect to a server that YOU have issued a certificate to. This is a useful way to control licensing. The server certificate expires when your license expires. The user can't simply extend use of the product by getting a publicly-signed certificate. They will have to come back to you, pay the license fee, and get a new certificate for their server.
No, you shouldn't use the same certificate on multiple servers. The whole system wasn't designed for that to happen, and it could cause all sorts of confusion and unintended side-effects. A certificate has to be issued to a particular domain name or IP address.