Leave existing forum and add a few features.
A Google search box, so it doesn't need to exactly match spelling.
Easier multi post replying.
Is there a way to reference a specific post without quoting? I couldn't manage to generate a link.
Mobile layout.
View PM's as conversations.
Add a sort feature of "mentioned" (called "you") like Tapatalk has. Not just unread replies, which aren't really replying to you.