Dear god why. What is the point of using the web if I'm going to target specific browser engines only? I may as well write native apps and target specific OSs only.
If your idea were implemented, I'd expect that in 30 years someone will propose the meta-meta-browser so developers can choose the meta-browser that hosts their chosen browser engine.
If your idea were implemented, I'd expect that in 30 years someone will propose the meta-meta-browser so developers can choose the meta-browser that hosts their chosen browser engine.