Nice work! Great summary of Byteball networking. I like the network diagram with all the different roles and how they are connected.
Although wallets have a primary hub, full wallets are actually connected to many. Hub addresses are sent around and each wallet connects to a bunch so if one goes down, another takes over.
In Byteball the hub/wallet/oracle/witness roles are a little fuzzy since they all base on the same core library, so for example a full wallet can act as a hub an oracle and a witness all in one.