Momoe,
Thank you for the article.
I agree with Elliot Hentov that dual interest rates for loans and deposits would lead to all sorts of financial engineering, either explicitly or through side effects. Perhaps it would be worth it, if the stimulus were genuinely needed during a crisis. But negative interest rates could also be a way for a sovereign state to "kick the can down the road," avoiding difficult decisions today and leading to default tomorrow.
Rob
P.S. I like the graphic for the article. Lemonade indeed!