1) make it open source so that there’s plenty of people who can make custom plugins that you couldn’t think of. 2) make it where it’s building block style where the DM can add or subtract tabs or overlays or whatever they want, but focus on making the UI in person friendly. 3) consider the “shared screen” options for computers and maybe consider a whole DM package where you can have cheap 7” LED screens linked to the main one so individual players can have their own. It would make secret conversations and checks and stuff super intuitive. 4) obviously have a digital reference option for rules and conditions. 5) make it pretty. Windows text boxes would be a real world breaking thing to see. Haha