I'd probably do this by observing the super_attribute select boxes on the product pages and on change, checking if you have all the values for all options of the product. With this information, you may be able to update your reviews.
if you need more information about the particular product, you can use the IDs/values of the select boxes and look at the spConfig javascript variable that's on the page which includes more information about actual product IDs.
One note though is that unless you have a very large number of reviews, it's probably worth showing review options for all variants of a product. Otherwise, you'll likely to have very few or worse no product reviews to show.
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