Not exactly what you've been asking for, just food for thoughts.
This is how I managed to disable image loading in chrome WDS test running under Jmeter:
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// Chrome magic to disable image loading, speeds-up the page loading over network,
// somewhat lowering the CPU load on browser side.
// Goes directly to Chrome's settings page, where Chrome set focus in search input box.
// Does TAB TAB ENTER to turn the lever from "Show all (recommended)" to "Do not show any images" position.
// Doing it "the right way", by clicking the lever by it's element locator does not work on settings page.
// Note that this should be done before calling "WDS.sampleResult.sampleStart()",
// as the time spent in settings page is not related to sample execution time
WDS.browser.get('chrome://settings/content/images')
sleeper.sleep(quartersec)
WDS.browser.switchTo().activeElement().sendKeys('\uE004\uE004\uE007');
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