If you do this for a living then I suspect you don't make a very good living.
This isn't for commercial enterprises to bring product to market nor does this burden anyone with losing "precious months" getting an OS running nor is the processor in this inherently "vastly under-powered" nor does $5 dollars of BOM cost translate only into $5 in product cost. None of your points indicate that you understand what a "viable business plan" is.
No one is late to the IoT party yet. It's not clear there's even going to be one.