The helmet CAN'T light the area because of limitations of the mc engine.
HUD tied to the helmet and trigger that occurs when player wears X item its basically the same shet. Read properly next time plox.
Says who? A client sided light is not that difficult to code, and as far as i know does not break any sort of limits.
Go look at the dynamic lighting mod, its client sided. Client sided lighting of an area also exists in Zombe's mod pack.
Really the only problem with this would be compatibility with other mods if you wanted to use it.
Mob highlighting is also very much possible, go look at Zombe's mod pack.
Also, the minimap thing has been done before. (possible merging between IC2 and a minimap mod?)
If a minimap cannot be done, then perhaps a built in FPS style compass at the top of the screen?
Then, onto ore highlighting... I assume you didn't mean an actual x-ray type thing, but a thing that just points out to you that ore is there so that you don't miss it.
I think that the helmet should be able to be charged in an MFE, but it takes 1 million EU to fully charge it, as to power the various functions. You could also be able to turn certain functions off with a GUI so that you can preserve power (you want ore highlighting, but not increased brightness)
Just a few ideas, i like your idea, and maybe it will get added?