Best to use 3 core SWA if exporting the PE, IMHO. That way there's a high degree of integrity in the connection, as it's not reliant on the galvanised steel wires always providing a very low impedance connection. If the installations are going to be wired with earth electrodes, as TT, then the CPC from the CU in that diagram would go to the earth electrode and the armour CPC would be isolated from the installation.
Inside the box (would need to be a reasonably big one) you'd just have two Henleys (one for line, one for neutral) plus an earth block. The earth block needs enough ways to accept the various CPCs, so for the set up above it would need 5 ways. If really stuck for space you could use a double decker Henley, but personally I'm not a great fan of them, and much prefer to keep the line and neutral terminations separate.