IIn addition, upgrading to carbon cranks and carbon saddles reduces weight by more than 1 kg.
Saving 1kg by replacing the crank and saddle seems to me impossible.
The lightest carbon crank like the THM Clavicula SE will maybe save 200g.
The lightest saddle like AX Lightness weight at least 65g and will maybe save 200g too.
These two components cost about.. the kickstarter price of Helix !