What is the problem you are trying to solve?
Liferay almost supports Google Merchant as it is visible under control panel. However, it is not actually implemented. Google Merchant is widely used product among ecommerce-customers and official support for it would be beneficial.
What is your project about? (e. g. Intranet, Partner Portal, Enterprise Website, etc)
This would be needed for (B2B) commerce solutions.
What is your proposed solution?
Liferay should support Google Merchant-integration Out Of The Box. There are other ecommerce platforms that support it, which give them competitive advantage.