I suspect the big issue here is that macOS has far fewer restrictions on its use than iOS does. So Apple would need to either lock down macOS, or open up iOS. They can't lock down macOS because of professionals, and they really don't want to open up iOS.

I don't think iPads would need to run "Mac OS", just quite a few artificial restrictions on iPadOS would need to be lifted. I need to be able to install software myself on the device - be it only a small shell script or python program - and most importantly, I need to be able to share files between programs in the sense that several programs need access to the same file and can interact with it.

I don't think Apple would ever bring full MacOS to the iPad. I could imagine them allowing M1 native Mac Apps to run on the iPad tho.

Since the iPad and the Mac use essentially the same CPU now, why not allow Apps to be cross platform between the two? I know you can run some iPad Apps on the Mac, but why not the other way?

If you could run Mac apps on the iPad, would that hurt mac sales? Possibly. Although, I could imagine many non-mac users would buy an iPad if it could run VS Code.