1. Jaime/Brienne (whichever is first, although I think Jaime is more likely) would be the main one as I'd really like to find out what is happening with Lady Stoneheart.
2. Arya - I really liked the Arya/Mercy sample chapter so will be looking forward to reading that one in the full book as well. It will be interesting to see if there are any major edits/rewrites to the sample chapter.