I'm not certain whether there's a straightforward way to disable disk encryption, and I certainly can't recommend it. Do you currently use the after-reboot command to bring the machines back online? An alternate avenue to explore would be to consider automating that command.
For instance, you may be able to set something up to run that command automatically whenever the machine is turned on. In addition to mounting the encrypted drive, it will perform a number of additional checks and start the supporting services. I expect that even without the encrypted drive, something would need to be run for the server to come fully back online.