Air defences are difficult to overwhelm. Gaza/Hamas recently tried to overwhelm Israeli missile defence with primitive rockets with very no success. The rockets were very primitive but had the advantage of a short range, which is harder to defend against. OTOH, the intercepting missiles cost orders of magnitude more than the offensive rockets, so it might be possible to drain the ammunition supply.
"loiter over an enemy airspace" is only possible if you already have aerial control.
Overall, armies are conservative. It's dangerous to try and build a strategy around fighting styles that have never been tried at scale.
It's probably worth researching though.