That is an interesting question, and I think it is a lot more complex than people think.
As I understand it, there are 3 phases to the spark.
Breakover. In this phase the voltage builds up across the parasitic capacitance within the spark plug, across the electrodes. The electric field ionizes the molecules and creates streamers creating plasma channels. While the conduction builds up, the impedance decreases dramatically. The result is several hundred AMPS of current. i = C dv/dt. So even with 40pF of capacitance (tiny), with 10kV and 2ns you have 200A of current flowing during breakover (but only for 2 nanoseconds - only 4 mJ)
Arc Phase. During the arc, the voltage across the electrodes rises to about 100V and about 100mA of current flows. The energy for the arc comes from the parasitic capacitances and inductances in the coil and cable and the characteristics are controlled by the external impedances (resistance of your cable is one). (Perhaps this is where the marketing claims about spiral wound cables etc come from?) The arc phase is sustained by electrons emitted from hot spots on the negative electrode (which is where some erosion might occur and talk of spark polarity is probably relevant).
Glow Phase. When the current drops further (<100mA) the voltage rises to 300-500V for a few milliseconds. This energy is delivered by the coil and limited by the cable resistance. Usually 10-100mJ of energy.
So different parts of the system are critical to different parts of the process.
To get more energy into the spark, you need more efficiency in the ignition circuit. Which means less resistance. So less resistance is good in this respect. (More energy goes into the spark, less into heat in the cables etc)
However, EMF or EMI is related to di/dt and dv/dt. That is the rate of change of current (or voltage) with respect to time. Therefore, in another sense, the lower the current the better, which results from higher resistance in the system.
But … the current in the secondary can be modelled with an LR circuit, where there is an exponential component e raised to the power of -Rs/Ls*t, where Rs is the combined series resistance of the coil secondary, the cable and the plug and Ls is the secondary inductance of the coil. Therefore, increasing anyone of those resistance results in a FASTER change in current, but lower overall current (and lower overall energy). Higher resistance results in shorter spark (glow time), while lower resistance makes for longer spark duration. To complicate matters, the effective resistance of the spark gap is an exponential function, with high resistance (>50k) at low current (10mA) and low resistance (<1k) and higher current (>100mA). So the spark is effectively changing resistance during the event.
The solution is a compromise.
The whole system is interrelated, with the coil secondary inductance (and resistance), the cable resistance and the plug resistance. You can bet Mercedes knew what they were doing using low(er) resistance wires. I would guess they were controlling spark duration with a certain coil to make it all work at a rated rpm on a V12.
If it were me, I’d try the wires you want and put a scope on the primary to “observe” the spark duration. This is also how you can find weak coils when dealing with COP systems (short duration sparks).
I think there are also other issues at play, but this has gone on long enough! Sorry.
Anyway, the real answer is to use Coil On Plug. Hopefully someone out there is trying that. They still tend to use resistor plugs (or have resistors in the secondary path). There is a Ford coil DG508 that is common on Crown Vic V8’s. Cheap and cheerful. This seems to have the perfect angles to fit the V12 with the fabrication of a small bracket.