hmmm OK. Well, unless you totally separate the greenhouse and put independent systems in the greenhouse then I don;t think your going to be able to accomplish what your looking for. You can solve the lighting issue by removing the shade cloth during winter. I will more than likely remove mine. That will increase the lighting. What is wrong with keeping the plants that go dormant outdoors. Then you only have to worry about the ones you want to keep growing? You would be able to keep the temps right for growth and with the shade cloth removed they should get enough light. It is going to be less than sumer, but would save from having to use lights. The only time growers use lights here is when they are getting an orchid to flower perfect for a show or picture. They use a HO light to get the plant to turn all its flowers to the light. That is how they get the phals in magazines to have all the blooms facing one direction on an arching spike. I don't think you should need the extra light just for growth, and since you say that you rarely freeze then what is wrong with building a small cold frame outside for your dormant plants? Then you can use those vent openers to lift the lid on the cold frame, but it would close at night or when it got real cold? I dunno these are just suggestions. I leave my sarrs and things that go dormant outside year round with no cover, but that is me too.
What is the min temp you want to run? I stay around 55 to 60 with mine.
I hope I gave you some suggestion anyway. Dunno how much good though. To achive everything you want though I think your going to have to run two setups set to different things. Since your trying to accomidate for two different growing conditions. Now you may be able to do it if your willing to compromise on cooler temps for the nepenthes so your temperates can still go to sleep. Other than that I am out of ideas.