Yes, that sounds great! I think that trusted assertions and a DVM-like API (using CVM) would be sufficient for a wide range of use cases. Trusted assertions alone wouldn't be enough for the case I mentioned earlier, where you encounter a user who doesn't have any assertion attached. To get the score in such cases, you would need to call a service requesting the score for that specific user who doesn't have any assertion attached.
The search interface API we already have in Relatr is quite straightforward. It is specifically designed to be unopinionated, just a required 'query' parameter, which is a string. There are other parameters, but they are totally optional.
Regarding the interface for the API, yes, it can be exposed in different ways. I like what Profilestr is doing by exposing a REST API and leveraging different WoT providers under the hood, currently Vertex and Relatr. In the case of Relatr, it is designed for CVM, which already provides all the primitives for authentication and other requirements for a solid user/service interaction