Daisy can marry the footman, still become a teacher because it's a modern marriage. She will discover dyslexia as a result of the love she has for her husband, thus make her fortune. Time will pass and the Grantham's will be unable to maintain the house. Daisy will buy it and turn it into a school for dyslexic children but provide the Grantham's with various grace and favour cottages.
Alternatively, Daisy will marry the footman and be a happy teacher at the village school. Lady Mary's new husband will transpire to be a whizz at business. He and Tom will persuade Lady Mary that open days will both enable them to remain at the Abbey and make a small fortune.
Lady Edith will come out of the shower and find Michael wasn't killed in Germany but has come home to make her and Marigold the happiest people on earth
Thomas will meet one of the gardeners (see various posts above about the missing gardeners). They will fall in love, all the Grantham's and the Dowager will be thrilled and delighted. Thomas and gardener will live in grace and favour cottage with Thomas coming into the Big House daily to care for the growing group of Grantham children.
I could go on, but you'll be relieved to know I won't