Backstory: Physical product companies are always looking at ways to acquire new customers.
The Idea: A platform to swap box space with other companies.
Deep Dive: You would build a platform for people to advertise their box space (market, rough size of customer base and product range). Users would be able to browse other companies and connect to work out a deal to swap space and/or purchase space.
Validation: There is a lot of upside for both companies in this platform. If they both think their respective products are complementary then it can help enhance their customer's experience with a discount. You could MVP this by cold calling companies and brokering a deal to prove the concept.
Monetization: You would charge a fee from each company in the deal.