If you are putting in a two way radio into your helmet I wouldn't think it would be too mard to wire. Granted, I am not an expert in these matters. But I think it would work with a minimum of hassel. Just have the radio secured in your pack somewhere, like you said and get something like a throat mic or headset to run up the tubes from your pack. Most headsets for two-way radios that I've ever seen have a push to talk button on them so you shouldn't have to worry about reaching the radio to talk to your vode. You could even get yourself a wireless headset of some sort, but this would probably be much more expensive.
As for the camelback, depending on the size of your pack you could have a very big water bladder hidden inside to keep you hydrated on those long troops. Then run the tube up to sit inside your helmet or just tucked inside your neck seal. That way you can get a drink without having to take your bucket off.
I did a simular set up with my camelback water bottle that hangs on my belt... when I get around to making myself a pack I will be upgrading to a larger water bladder to hide in the pack too.
As for the lights, your local electronics supply store should have all you need to wire those up. Here in the states we have Radio shack, I'm not sure what the german equivalent would be though... I am a beginner when it comes to circuits but I managed to wire up two helmet fans for my bucket with switches for each... and so far nothing caught fire or exploded so I must have done it right. LOL
Good luck!
