Different Power Networks / Better Power Supply

Ability to set power to different 'Power Grid's through a drop down, so that you can keep a backup generator that will only power specific networks to keep the bare minimum going in times of emergency.
I know the devs are conscious of making a complex mess of power poles and lines, but I find the current method of power distribution to be far too vague, and it would be nice to have more control. i,e, setting a machine to 'power network 2' that uses excess steam normally from the main 'power network 1' chain, but has a 'priority 2' diesel generator set to 'power group 2' in case 'power network 1' goes down, keeping core services like Ore stations going.
Failing that, just having a magical 'Export power to' like logistics routes, within the power generator UI, so i can link things directly.