Why not have vendors for thursday to saturday so it leave them free on sunday. And have sunday last a bit longer with a few more panels with closing around between 6 - 8pm that way they get to enjoy the con like any of us and the vendor hall already winded down and closed by saturday.
You still have your three days of vendors with the fourth just for every single person attending.
Also maybe we could have as well some people try to get a panel in, some new fresh faces that want to be involved with the community, I noticed that a fair few of the panels are almost ran by those that done it for years.
I would love to do one myself. Never done it but willing to give it a try
I tried to get one this year on the subject of backstories of original characters from how they came to be to the very meaning of the character itself.