Thanks for the feedback.
Unfortunately, this is not yet possible as ARC does not support the authentication I use to validate the Google account with my server: https://code.google.com/p/chromium/issues/detail?id=297129
Seeing that the issue was open for two years and nothing happened, I have my doubts that it will change in the near future.
In the meantime, if you really want to use the app in ARC, you'll need to convert your Google sync account into a Deliveries account by using the reset password function (make sure to disconnect the Google account from all your Android devices in the app first).
Lastly, I cannot offer the pro version for ARC as the license check relies on Google Play completely. I might decide to sell it on the Chrome Web Store as a separate purchase in the future though.