Some of the things on my current Zap to-do list....
1. Provide a function to left-right swipe the notification menu and sidebar in and out on handheld devices.
2. Provide a UI for creating polls instead of (or in addition to) using markup code.
3. Integrate a drawing editor for Zap's inline SVGs so you can easily create diagrams/doodles in your posts.
4. Provide a way to link tags or categories to your collections (sub-channels) so that anything with a #steampunk
tag goes to your steampunk channel.
5. Bring back a wysiwyg editor for at least the common stuff; although many of us treat the post editor as a shell or command line.