There's little chance of that working, taking both off and attaching the vacuum to the round hole then blowing with a compressor line through the square one might shift a little dust, but again I doubt it.
Breaking the electrostatic bond to the lens would be quite difficult, it's unlikely to just blow off.
Heat up the lens and prising it away from the body, breaking the seal will allow you to clean the inside of the lens. However, you'll run the risk of fracturing something and you'd need an acrylic sealant to rebond the lens on afterward.
Overall it's totally not worth it unless the headlight has failed an MOT, which it's not likely to anytime soon.
I stand corrected, good tool invention there - my luck would be the thread would break and leave the 10p rattling around inside the headlight.