To implement your own Selenium driver, implement com.saucelabs.selenium.client.factory.spi.SeleniumFactorySPI. The Selenium client factory uses the service loader pattern to look up your SPI implementaions, so you need to list your implementation class accordingly. Check out @MetaInfServices for auto-generating the META-INF/services file.

Your driver should claim a specific URL scheme, like other existing drivers do. The interpretation of the rest of the URL is up to you. See the javadoc of the SPI for more details.