Nick here from Shopify.
As you mentioned your best bet here would definitely be an app from the Shopify App Store. There are quite a few different "Recommended Product" apps in the app store which all have the same primary feature in terms of setting up recommended products, but they would have different sub-features in terms of where the products will be placed or which products should be labeled as "Recommended". It might be worth your time to take a look through the different apps and find one which you resonate with and feel could work for you in terms of what you're looking for. Let's take a look at some of the options below:
Hopefully, this helps and you can find something which works for you.
All the best, Nick
Ah ok, I see what you mean now.
From what you are describing it seems like this is something which would be quite custom and specific. If you don't feel like one of the apps would be able to help you with this, I'd say your best bet would be to reach out to a Shopify Expert to see if one of them could build something customized for you. You can see the Shopify Expert directory here.