I think the layout should be similar to the website now. Have the lightning at the top to see the most recent posts, the bell, DMs, your profile setting and the search bar next to it. The mobile page on CIS is actually so nice to use, I wouldn't necessarily install an app.
Of course you can do some stuff with the design, but don't go overboard. Functionality is the most important, people won't use an app if it doesn't work correctly.
And don't mess with the colors on the dark mode. Just keep that.