I would tend toward your system Paul. I don't usually 'pipe-up' the whole internal installation, just the drops, unless it is;
a) Requested, or
b) Easier to fix that way ( steelwork etc ).

I install a dedicated CCU with EP ( metalclad) and run SWA underground - or overhead if required. All bonding, etc, is carried out in the shed as for any other installation.

If hindsight were foresight, we'd all be millionaires!