OP
Gardner
So as I understand it now, you are designing an installation outside the UK, where UK building regs do not apply, where the supply is not of the type provided by UK DNOs, but you wish to comply as far as possible with BS7671 or use the standard as the design framework. A lot of head scratching could have been avoided if this had been explained in the OP, as this is a forum primarily for UK electricians working to UK regs in the UK.
More along IEC60364, but I am using BS7671 to to verify my thinking.
You substitute Schuko and radials for BS1363 and rings, to avoid the problems mentioned above, and provide DP OCP and isolation throughout. And then we get to 2-way light switching and I am going to hide behind a pile of DP relays!
I am still leaning toward light fittings only needing single pole isolation when dealing with GU10. I do not see any reason to install DP switching unless occupants or users will come in contact with lives parts such as service, testing or modification. In that case a DP MCB will do the job as power must be disconnected before attempting such.