Backstory: Everyone was buzzing with Kayne's recent tweet storm that started with his idea of "Y Combinator for the Music Industry." Taking the concepts learned from Y Combinator you can apply it to different disciplines and niches. 

The Idea: Y Combinator for eCommerce.

Deep Dive: Focusing on eCommerce, you'd have to host space in a mixed use area, warehouse space for deliveries and shipments, storage and office space. One of the largest line items for eCommerce stores is shipping fees. You could create a parent shipping account to get discounted rates for all companies inside your incubator. Given you'll provide better rates than startups could get themselves, you could structure the deals to take a percent of shipping and a smaller equity stake to create a more enticing offer and reduce your risk.

You'll also want to create partnerships with packing supply companies and physical product design agencies. This will help get your startups off the ground quicker. 

Validation: Y Combinator is clearly winning, if you can create a repeatable process for building, launching and growing eCommerce companies, you can win with this model as well.

Monetization: You could go the same route as Y Combinator and invest capital for equity. Additionally you create a shipping account for discounted rates and take a small percent of each shipment. This would help manage cashflow.

Steps to Launch: Ideally you would have exited or have a profitable eCommerce business. This should give you enough clout to raise a small fund to begin investing in these new eCommerce startups.