The challenges I found with FHE in practice (where I have been asked to anticipate its availability as part of system architecture) are that even with demo code available, without some certification body acknowledging proofs of its security, and blessed by a risk nullifying entity like NIST, it wasn't going to get traction.

I like this article's crypto wallet use case, and it may be worth codifying transactions that FHE protects. The {who, what, when, where, why, how} of a transaction has a lot of data, and what this SpiralDB does is protect {what}, although {who, when, where, why, how} are available, so you need to articulate the use case.

The one I worked on was for health information, but that case is essentially nullified now, as the pandemic was leveraged to squeeze the data toothpaste out of the tube in major jurisdictions, and so the data sets FHE was going to be a big solution for have been accessed using a political/process solution without the limitations of a technical one. The main use case for FHE was to faciliate individual privacy, which is essentially a limit on state discretion and powers that facilitated data access through strict legal frameworks, but a lot of data governance was completely compromised and gutted over the pandemic, so I no longer foresee demand for FHE in this new era of aggressively technocratic policy where the reason to use FHE isn't enforced. The tech is inseperable from the policy in this domain, and the rug has been pulled out from under the policy, imo.