Your first sentence is the most idiomatic.
As for emphasis, as you mentioned in your comments, you can indeed reorder your sentence and place what you want to emphasize in initial position. However, with a subclause you should probably choose another way of emphasizing since long parts of sentences are usually put at the end of the sentence. Also note that new information is usually also put at the end of a sentence while known information can normally be found in the beginning or the middle of it.
In your first sentence, you can see that there is a provisional subject it in order to make the sentence more readable by allowing the long phrase to be replaced to the end of the sentence. If you then reverse the order again by placing that long phrase at the beginning of the sentence, your sentence becomes less pleasant to read.
There are other ways to emphasize phrases, have a look at this:
- What is hard for me, is that I can't see you.
- I can't see you, which is hard for me.