I was thinking of trying some modding myself.
It's always bugged me that redstone devices just 'work' with no power source. I really like the idea that you have to power your devices with something in order to get them to work.
I was thinking changing the way redstone torches operate - in order for one to work, it needs to be near a 'power torch' (maybe like a redstone torch but blue or yellow) - this is connected directly to a power source by a trail of redstone.
The power source could be a number of different things:
a generator which needs crafted fuel to operate
a battery which has previously been charged up from another power source
a windmill or water wheel
So for something simple like a plate which opens your front door you'd have something like a waterwheel in a stream, the hub block of which would be connected with redstone to a power torch next to the door circuit. As long as the redstone torches that made up the circuit are within, say, 6 blocks of a power torch, they'll work as normal.
A power source would also have a finite amount of power it can deliver, so if you tried to power too much circuitry from a single source, the circuitry wouldn't work (maybe have it short on and off if you only slightly exceed the demand)