Product Idea: Cross-Promotion

I finally settled on an idea I want to test out. This felt so much better than if felt when I used to come up with product ideas in a vacuum. I collected all these insights from my customer interviews which is giving me a lot more confidence in my product ideas. Even if this idea doesn't work out, it's a much better starting place than how I used to do it.

So what's the idea?
A lot of newsletter creators I spoke with have tried to do cross-promotion in the past but found it difficult. I'm thinking if there was a cross-promotion marketplace it would make it easier for creators to find matches for cross promotion.