What's the next big thing on Android? For years Widget Locker users had widgets on the lock screen... then Google added this (sort of) in 4.2... CyanogenMod's power controls (toggles in the notification pane) came to stock Android in 4.1 and Sense/TouchWiz even before that.
I'm not a developer, but I have an idea. If somebody makes it, I'd pay a fair price for it, and I believe a lot of others would as well.
Fullscreen Widgets would be a customizable widget you'd add—if you've used UCCW or Minimalistic Text, you've got the right idea. However, the widget would take up the entire screen, so you would have to create a new page for it in your launcher if you don't have one already.
When you create the widget, you basically get two settings. One, you can define the trigger placement and thickness. If you've ever configured Pie in a custom ROM, or the LMT Launcher, you've got the right idea. The triggers allow you to go to the page to the left or the right, bring down the notification and quick settings shades (two triggers on top) and bring up the navigation ring from the bottom. Swipe within a trigger, action goes to Android or the launcher. Outside the trigger, you're working within the widget.
The second option lets you populate the widget. The widget can contain any number of app icons and widgets that fill a page. It can also include a single fullscreen app, like Facebook or Chrome. Thus, fullscreen widgets can scroll, as long as you don't touch the triggers. Fullscreen apps are loaded when that page is first accessed. Say you turn on your phone, and launcher page 1 is your apps, and page 2 is Facebook. When you first swipe over to Facebook, you get the blue Facebook loading screen, then it loads and you can use it like normal. If you're not on page 2 and the Android system kills the app, swiping back to that page would open it again like normal.
Credit where it's due: the built-in browser in Lucid Launcher:
I'm not the developer, or affiliated with them in any way. But their browser did influence my idea. Also the Google Now launcher. I'd love to have Google Now on the left and Chrome on the right.