Single/Multi-Review Template auto-selected based on cart contents

I like the in-email review for the single-review template, but don't want to send out multiple emails if a customer orders several products. I'd like an option to automatically use the single-review template for customers with only one product ordered, and automatically switch to the multi-review template for customers that ordered several products.

Right now, we're left with choosing between three imperfect options: no in-email review capability, potentially spam customers with multiple review requests, or send a request to review only one product, even if a customer ordered several.