I am a seaon ticket holder and have never had an issue with someone sitting in my seat, but I often see people coming in and struggling to find one without a sticker. The stewards offer conflicting advice to people who have paid at the gate.
I also know there are a few seats close to mine with stickers on that are always empty. Would it be an option for season ticket holders who don't sit in their own seat to tick a box on their application form stating that they don't require a sticker on their allocated seat. That way there would be more available seats for pay at the gate customers that are not reserved. Obviously, at the busier all ticket games the season ticket holders would automatically be allocated their original seat.
Just an idea but don't know how practical this would be.