Suggestion 1: A cool idea would be to have a way to connect to your world(server or Singlplayer) via smartphone and be able to operate lights and even future machinery. This will require a mobile app of course!
Suggestion 2: There is this Minecraft mod called Buildcraft that adds quarrys that will mine for you. Item transport pipes would be really useful with this feature as well!
Of course with electricity comes power generators. Red51 could make a challenge by adding machines that require a higher power consumption than what a typical generator can output, and would require a higher-tier power source, which leads to my next suggestion:
Suggestion 3: Besides typical generators, adding engines that run off coal power and with the requirement of water cooling! Which would certainly give future water pumps a good use! (Perhaps start off with no water cooling for engines, then add pumps in a later update?)
Electric engines will be more efficient than a typical generator, by using less fuel and outputting greater power! Stirling Engines will run of coal and will output twice as much power as an electric engine.
The third type will be solar panels which would put out as much power as a electric engine(perhaps)!
The power source tiers would be as such:
T1 Generator
T2 Electric Engine
T3 Stirling Engine
T4 Solar Panel
Combustion engines would be much later cause oil refining will have to be a thing to make gasoline!
Suggestion 4: Adding features such as wire-management! In the build menu, there would be insulated wires that you can color that can be connected with a new tool, called the power tool(or power connector) These wires will have dynamic connection points(with reach limit) that can be placed by the player. The player will physically place and shape wires down, then use the point connector to shape the energy flow with the shape of the wires!