My suggestion is basically that all light in the game should either be produced by sunlight, or some form of fuel to generate a need to create a lighting network using luminators. I decided it would be fun, being an engineering apprentice, to do a few calculations to come to some sort of rational as to why certain variables should be set to certain things. The consequences of these suggestions will be that all light sources will either be powered by electricity or will run out of power. Those which do not will only produce a light level of 7 or below (You can see that way, but mobs can spawn).
Luminators produce light for an electrical cost of 0.25 EU/t and the output of said light is equal to one torch.
Coal contains 4000 EU which when used by a generator can supply a luminator to produce a torches light for 16000 ticks.
16000 ticks is equal to 800 seconds or 13.3 rec minutes.
My suggestion is that torches should last for a period of time which is proportional to the EU stored in a piece of coal. 13.3 minutes is silly however, and the calculation I just did wouldnt be wholely accurate. 4000 EU is actually the output of the generator, the closest I could find to a real life parallel of a coalfired generator is a combustion engine (Standard electrical generators in coal fire power plants use steam turbines). A standard combustion engine during its best period of a car drive will output 26% of its fuels energy as useful work. 4000 EU can be treated as the coals useful work. To calculate the actual EU stored we do:
4000 / 26% = 153.846 (1%)
153.846 * 100 = 15384.6 EU.
This is could be considered to be the chemical energy stored within the coal. Doing the same calculation as before to get the time in minutes of how long a torch would last at 100% use of the fuel as light we get:
51.282 minutes before a torch burns out.
For simplicities sake I would argue that this time should be 45 mins to 60 mins of time. This gives plenty of splunking time and enough for quick light when you need it.
Glowstone is a natural substance which "glows". Its light level should become 7, which allows vision at the expense of mob spawning. Lanterns are made from glowstone and also don't have a cost so they should also be set to light level 7.
Pumpkins shouldn't produce as much light as torches realistically and should also go out after the same period as a torch.
In conclusion I feel the above changes will make some fun changes in gameplay. The first is that light production is now balanced to how I feel it should be, where you can only have infinite light by supplying electricity to it. I know minecraft isn't a simulation for real life, but the idea for working for comfort tends to be a trend which brings technical minecrafters to mods like industrial craft. I personally haven't lit a candle or a torch since the power went out last year, and I recognise that I have to pay for my power if I dont want to go back to that situation. I think minecraft would be better off this way, and I think it is very doable if you have things like what is present in this mod (Electrical infrastructure for example). Second is that it makes EU production more necessary, instead of gimmick items and production increase you also have to generate electricity for light on its own. Be it in the form of lighting caves or for street lights and building lighting or otherwise (Also if torches run out, an electric mining helmet wouldnt be so OP anymore.). The final reason is that I think it would inspire more lighting networks using luminators, I rarely see them and when I do its basic overhead lighting for bases. I think they should be used for more than this.
So overall what this would entail is:
Change in light level for passive light blocks such as glowstone and lanterns.
A state change for lights which produce full light (Torches and Luminators) which is based on the energy requirements of these.
A config file change to allow for people to switch this feature off, fun for a lot of people.. but not everyone wants to work that hard for basic necessities.