we want to use the Google Adwords Connector to enrich our retargeting lists.
Unfortunately the user matching only works by matching the email adress. Is there any way we can change that to
the GoogleId which we use for example with the doubleclick connector?
The email match is a requirement on Google's side and with Customer Match you can only use constant variables for one-to-one targeting so an ID would not necessarily work and alas Google has a fixed template for Customer match, they wouldn't accept the DoubleClick cookie ID anyway.
The workaround could be as you said to use DBM to buy targeted display ads using the DBM connector and run highly targeted retargeting campaigns via RTB and not just Google inventory.
Hope this helps.