Although I cannot find that line item detail can be included in email, I did just finish building out automations to update deal properties based on line items.
I used a deal based workflow, then set enrollment triggers based upon line items added to the deal. In my case, I used SKU numbers. Ex: when a deal is associated with any line item where SKU = 1.1234, set property value for deal target object X to value Y.
For non-value properties, I have these fields update when the deal stage is known, then re-enroll when the deal moves to a closing stage to ensure changes are captured. For value properties, I have them update when the property is known, so any time the value changes it drives a re-enrollment.
This is using SalesHub Enterprise, not sure if that is what you are using. Hope this helps!
There is now a beta with limited applications called Use Associated Record Data in Workflows. However, you can only access one line item which isn't necessarily all that helpful.