Remember KDE Fiber? It was some of the best vaporware ever. Remember when whatshisface was thinking of making it use lots of plugins for customization?
Why not make that a reality? We make a web browser that isn't actually a browser at all, just a plugin framework? It's just a bare window to hang things on and the rest is plugins. This will include not just plugins similar to firefox addons, but EVERYTHING. The layout engine? Plugin. Javascript engine? Plugin. Want a fancy address bar that let's you do X? Plugin. Want vertical treed tabs that are color coded? Plugin. Want to change layout engine on a per site basis? Plugin. Want to use web extension plugins? Get the web extension plugin plugin. Like a nanokernel, the "browser" is just a skeleton to make sure the plugins can all talk to each other and work together. It's the fleshy plugins that do the actual work.