Extending software makes it more complex. As you keep adding extensions, the complexity grows until the app is unusable. Doesn't matter if it's built-in or a plugin, result is the same. But there is a proven alternative that works well.

Write completely separate small apps, and it's a different result. You get reliable functionality without an increase in complexity. Don't add a "file search extension" to your application (consider that if any other application wants this functionality, now they have to implement their own extension). Instead you make one completely separate app, called 'grep'. You then call that one 'grep' app, from any application.

It's a very old-fashioned idea to programmers who have only ever known custom-integrated REST APIs and microservices and giant monolithic frameworks. But this old-fashioned idea is the reason AI agents are even useful at all. They call those old-fashioned single-purpose external tools, and suddenly the agent has useful features, no custom extension needed.

Another thing you don't need: "a platform for platforms". There's already a platform designed to run interoperable applications. It's called an Operating System. It runs these little independent things called applications. They all have data object storage input-output access. Even internal communication between processes. And they're all compatible.