I would think having some way to turn on and off a connection would be nice. say if you had a teraformer that you wanted to be able to turn on and off so you could blow up an area then fill it again then this would be nice. it would be a block that will allow current to flow through if it is given power from a redstone source.
switch block
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In theory, you could rig up an unwieldy analogue to this with an Energy-O-Mat.
But I agree, Redstone power should be able to disable the conductivity of a cable block.
Then you could have something clever, like a machine that only receives power conditional to a coded array of levers.
I'm not sure if it would be possible with all of the cables though, IIRC redstone can only power opaque blocks.
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would be good to gave switch block, but for now you can use transformers for this