We size the transformer bund to contain a 26.5° oil spray from the top of the tank, radiator, bushing turrets, and the bottom outlet from the conservator. CIGRE brochure 537 says a spray angle of 30° from vertical is commonly used.
Looking at your drawing, oil from the radiator could spray...
As I believe you are in NZ, you could use the transmission company's service specification 07.23 (Work site and Mobile Plant temporary earthing and equipotential bonding of transmission lines) as a starting point.
I believe multiple single-point grounding can also be called sectionalised single point bonding, please see Figure 2.4 from CIGRE TB 797 below:
The sheath voltage limiter is essentially 'open', like a surge arrestor, so only one end of the cable is directly grounded. The sheath/shield is not...