I have heard it said that season ticket holders should get in on their ticket as they will have only had 18 games, rather than the 19 they signed up for. Unsure about this.
A split with 7 in each wouldn't be popular as you'd always have two teams without a game each week post-split for each of the set of 6 fixtures. I think upping that to 16 in the Premiership would be too many.