Make iframe click-through, but not the iframe's body

How can I make an iframe click-through, but make that iframe's body still be clickable?

I tried:

iframe.style.width = '100%'
iframe.style.height = '100%'
iframe.style.display = 'block'
iframe.style.position = 'fixed'
iframe.style.backgroundColor = 'transparent'
iframe.style.pointerEvents = 'none'
iframe.style.border = '0'
iframe.frameborder = '0'
iframe.scrolling = 'no'
iframe.allowTransparency = 'true'

and inside of my I frame I'm using the following css:

html, body {
    /* background:none transparent; */
    pointer-events:auto;
}

This results in body being visible (which is what I want), but it is click-through like the rest of the iframe. I want the body of the iframe to be clickable, but all the rest of the actual iframe element should be click-through.

The iframe is always bigger than the body inside of it.

Unfortunately I cannot access the the iframe content from the main site (so accessing the scrollHeight etc isn't possible), I can only change its actual source code.

from Make iframe click-through, but not the iframe's body