25kV insulators are needed regardless and it is probably cheaper to stick with standard parts for cantilevers, registration arms etc....
Well that depends whether you want to use more steel than China does in a year.
The entire parts range is pretty much junk at this point.
Every significant installation done with the new equipment has run hugely over budget and was/is behind schedule.
Things like twin Track cantilevers will require huge, expensive to install foundations to resist the overturning moment.
You can design an electrification system that has much smaller foundation requirements, to the point of probably being able to dispense with piled or concrete foundations entirely.
I am very interested in "rigid headspans" like those used in parts of Japan and on tram systems.
Imagine a headspan where the bottom span wire is actually a metal tube.
Also cantilevering weights on the back of the pole to conver (some) overturning moment to additional weight.
EDIT:
Ironically the simplest system to install could easily be wood poles supporting a lightweight top-member with cantilever weights outboard.
So the poles can be simply buried without concreting.
But overall..... if you can't get below £1m per single track kilometer, give up, we are done and the railway is likely doomed.