My apologies for the delay in responding.
I was inquiring internally to determine whether I had misunderstood the requirements for NTA4.
Turns out, I had. :-(
The 64-bit installation requires the use of the new datastore, and the datastore requires the use of 64-bit systems.
The only way to retain NTA 4.0 on a SQL Server instance is to install NTA 4.0 to a 32-bit system.
Is there anything I can do to help with the issue regarding the use of the new datastore?
I'm curious about the specific reasons for it being disallowed in your environment, and if this is going to affect other military installations as well.