I have to agree with jgreco here. That would cause a heck of a lot more trouble than it's worth. What attack vector exists that you're trying to prevent? Which scenario is more likely?
- A robber enters your datacenter. He dismantles your TrueNAS server and replaces the motherboard with an identical version, but backdoored with the secret ability to transmit keys for your SED drives to China?
- A robber enters your datacenter. He steals your TrueNAS server.
As a general statement, TPM being integrated in mobile devices makes sense. If someone stole your laptop, before TPM existed, they could pop your hard drive into another computer and dump it's contents without any sort of password. BitLocker + TPM solves that problem. In a server environment with a TrueNAS in a datacenter, with sometimes hundreds of disks, the risk of such an attack vector is infinitesimally smaller.