Earlier quoted context omitted.
The "MacPad" already exists. It's called the iPad Pro. It uses the M5 chip.
Except it doesn't run MacOS, and it doesn't allow you to install any application you want to - only those that Apple allows you to. And you're still forced to use Safari in every browser you install.
If you want macOS, you buy a Mac. You want iPadOS, you buy an iPad. And if you want an iPad Pro that can double up as a Mac in a pinch, you feel awkward while Tim Cook death stares at you until you empty your pockets.
In all seriousness though, I have an iPad Pro and a MacBook (as a lot of people here do I'm sure) and it would make a poor laptop. And how do you switch between macOS and iPadOS? I don't see a way to have that not be clunky because of all the different metaphors. I'd rather just have both (actually I'd rather just have the MacBook as the iPad sits largely idle, as I'm also sure a lot of people's do).