An AI extension, maybe like a thing that can learn, or something that will play your game and tell you what you could add

A Physics extension, maybe have it so we can have better bounces, or make it so it is easier to make platformers and stuff

3D extension, make it easier to make 3d projects

Color detector, a thing that can get what color it is touching, it would make things a lot easier.

That's all i got right now!

A Physics extension already exists. https://extensions.turbowarp.org/#:~:text=Sample%20Project-,Box2D%20Physics,-Two%20dimensional%20physics Box2D if your web browser doesn't scroll automatically.

a math extension would be really useful like with factorial, complex numbers, calculus blocks and constants like pi and e.