Are you installing this in a managed (i.e., with Universal Server) environment or unmanaged?
If in a managed environment, you can create a policy group with the whole disk encryption feature disabled. This will make those portions of the UI in PGP Desktop be hidden.
To enable WDE for these users - simply move them back to the policy group with the feature enabled.
Unmanaged is more difficult. The most obvious way would be to do it via licenses.