yeah, that's pretty much the structure, except I do intend to quickly move it towards where you cut out that steemit part between the clients and the rpc nodes - the RPC nodes will directly serve up the web application, as soon as I can make it that way. 

There will then be many possible web access points, anyone can run, simply by hosting a simple, easy to install interface, and this interface will basically just keep a cache of all available RPC nodes, that are kept up to date, and randomly assign them (or maybe, better, chosen by the client side according to the RPC with the lowest ping).

There will never be a Calibrae corporation registration. RPC operators will, however, be free to run their own cluster systems, and register corporations, and get banking charters, if they can, so they can become direct fiat gateways.

Calibrae will remain fully decentralised, though as an organisation, centering around the database it lives on.