Firing Google Analytics Event via IMG URL

I would like to fire a GA event on a third party domain without putting any tracking code there. One option is to track this using Google Tag Manager, but we only need to track one simple event and the third party might not need to track code or iframe.

I am assuming I can encode GA event information into google-analytics / url? etc and assign it to the src attribute of the IMG. The third party then needs to post the image on their site. This seems to generate all the information needed to generate the url: https://developers.google.com/analytics/devguides/collection/protocol/v1/parameters

I can pass the client visitor id (the value of their _ga cookie) from my source domain to a third party domain using the url parameter in the hyperlink and then populate it into the url of the IMG url. This seems to be a must.

Is there something I am missing? Will this work? Any long term problems?