One thing I've found lately, is that these pretty-but-way-overused name (like
Olivia,
Sophia,
Emma,
Madeline, etc) can have a whole new life breathed into them when they are put in the middle name spot. So yes, I agree that
Olivia could make a very good and unexpected middle name.
Personally, I also really love
Olive, but they are both nice.
Willow Madeline Olivia is too long for me. I dislike three name combos as a general rule, but especially with this many syllables. Also, this combo has a lot of L sounds and I don't think it flows super well. Plus all three names feels too trendy. I'd prefer a more rare first name paired with
Olivia.