Losing PR does not necessarily mean that you are being penalized by Google for keyword stuffing. Have you noticed a change in rankings or traffic?

It sounds like the cause is between an inflexible CMS and a client who has their own ideas. Would changing the product title really hurt their traffic in e-commerce engines? Are there any products with traffic that the client would be willing to test? Can you gather any data (e.g. traffic/competitive data for a more ideal product name) to show what they're missing out on?

Some projects include more diplomacy, convincing and teaching than technical knowledge or link building. This might be one of those.

Without seeing the pages in question, I can only offer my best guess.

Hey there,

Perhaps you could clarify exactly how the CMS structure is creating a "keyword overkill." Are links from the category page to the product page forced to use the same text? Must the anchor text include the category name? Is the CMS pulling product specifications into the anchor text? Does the CMS just insert the word "body" into product names with reckless abandon?

Google tends to be a forgiving with repetitive product names on e-commerce sites. How do you know that keyword stuffing is the problem?

Recommending a fix is going to be next to impossible until we better understand the problem. Based on the conjectures I'm making, I can't imagine how a canonical would help. If the CMS is getting in the way, you may need to focus your energy on convincing them to make the change, rather than beating your head against a wall while pulling in a different direction.