Importing reviews into a website seems to be against Google's guidelines:
Sites must collect ratings information directly from users and not from other sites.
Review Guidelines for Local Businesses
However the wording is fuzzy here. Do they mean that (1) you need to collect reviews directly through your domain, or that (2) you can use external tools to collect reviews on behalf of your domain and then import them, just not steal reviews from other services? My hunch says the former.
That said, other SEO players in the industry are getting away with it as we speak, so it's likely that you can too. For example there's a service called TrustPilot that's one of the biggest in the industry, and they offer a review-to-structured-data import tool. My logic here is that since they are a trustworthy SEO company, they would not offer the service if it didn't work.
If integrated correctly with schema.org rich snippets, the imported non-Trustpilot product reviews can have SEO benefits. Remember that duplicate content has a negative SEO effect. We recommend only showing individual reviews in one place.
So as long as the reviews you import are not duplicates from other parts of the internet, it could work out favorably for you. The worst that Google would probably do is just not show the review snippet. It seems very unlikely to me that they would levy a manual action, but it's not impossible.
...just don't hold me liable for what you end up doing!