Automate Google Chrome extension installation
You may be able to use external extensions. You will need to generate the external_extensions.json file or add your extension to the registry.
http://code.google.com/chrome/extensions/dev/external_extensions.html
Have a look at auto-updating. You would install the extension once, setting it to auto-update. When you get a new build of it, it should auto-update when chrome next checks. The default interval for checking for updates is several hours, but you can perform a manual update (from the extensions page), or by launching chrome using
chrome.exe --extensions-update-frequency=45to set the update frequency to (for example) 45 seconds.
Your build should just update the extension xml file to let chrome know that a new version is available.