If James V had married Mary, he would probably have to agree a marriage treaty similar to the one Philip II of Spain signed when he married Mary in OTL. James would enjoy her titles for as long as the marriage lasted, all acts of Parliaments would be dated with both their names, and Parliament would be called under the joint authority of the couple. If Henry VIII dies in 1528, then any regency council would surely be composed of the Duke of Norfolk, the Duke of Suffolk, Cardinal Wolsey, and Thomas More. Wolsey will probably live longer in this scenario. Since Wolsey had a hand in the early education of Mary, I suspect she would use him as both an advisor and as a counterweight to the other members of the regency council. In 1525, Henry VIII made his natural son Duke of Richmond. Henry VIII granted Richmond numerous titles and offices, which gave Richmond an incredible base of power. If Richmond’s early death in OTL is avoided in this scenario, then his attitude toward James and Mary could determine how smooth their rule over England would be.