How much space does this take up on disk? I imagine it is still relatively small, right?

Would this be something a mobile relay could index, like Citrine? Maybe not index all pubkeys’ 10002s, but an extended WoT, like follows, their follows, and one more layer deep of follows.

We’d end up with something similar to a DHT, but with each mobile relay only indexing the 10002s of those they are likely to want notes from regularly, so they have to make requests to the larger indexers far less often.