I'd say before you utilize the canonical element It might be worth the dev time to choose one or the other and have the CMS configured to either drop the '/content/' in the urls or just stop creating the versions without '/content/'.
I'm sure you've already considered that, I'm just saying that is the way I'd go. Remember, the canonical element is just a suggestion so won't guarantee the results you are after. Better to just address it in the CMS or stop creating the duplicates. Good luck!
