I am currently building two sites for my client that adress slightly different audiences (reg. tone of voice, etc.) but basically share the product portfolio lying underneath of it all. Therefore, it would be really great if I could reference a collection (here: products) across these two sites without having to load and maintain them twice. 

In my (naive) thinking, there are two ways to do this. Either build and maintain the collection in project A and reference to it in project B. Or have an independent collection that sits below the "sites" layer and reference to it from both sites. 

What do you think? Doable at all?