The answer to the question will a Juniper die inside is yes it will, and quite quickly. The person who said it could be was lying to get a sale. If a plant is wanted inside then a species that will cope should be bought not one which will suffer and die.

My last post in this thread.

If you think you can do it, by all means go ahead and do it.
Please, please don't forget to post a picture of your three in one year to prove we were all wrong.

Your points about the natural and ideal conditions of junipers and the stress they experience when in different conditions are good. That all makes sense. However, it seems to me that much of bonsai is unnatural and stressful to trees. It is unnatural and stressful for trees to be confined to tiny pots, pruned, repotted, and bent and shaped by wires. That is why "if you have never killed a tree, you are not doing bonsai."

That being said, Mimo and tubaboy make good points about trees and mostly constant conditions. We can clearly make the trees adapt to a lot, but perhaps it is too much to ask them to keep adapting back and forth. If it can be done, it certainly sounds like much more difficulty and effort than I was looking to take on. So I may just relegate this juniper to my apartment balcony and call it a day.

you said it, it is too much to ask them to keep adapting back and forth.

i have trees that even if i simply rotate them they will drop leaves i couldn't image what they will do if i move them once a week. Your balcony will be a good place and you will still be able to enjoy your tree at home.