I thought that a necessary part of the "Double Irish with a Dutch Sandwich" was that a company in a tax haven can license IP to its subsidiary at an arbitrary price. Therefore, that company can offset any profit its own subsidiary might make.

To do this requires two things:

1. That the license arrangement with the subsidiary is unique to that subsidiary.

2. That the license fee can be set to any value at any time.

For more concrete assets, for example a bag of coffee beans, it's easier to see when a parent company charges a subsidiary a different amount than the market rate. However, there is no comparable market for IP, so it's harder to see what a "fair" price for a copyright, trademark or patent might be.

One option might be to tax all IP licenses at the corporate tax rate. Another would be to adopt a "most favoured licensee" rule, requiring all licensees to pay whatever the cheapest rate was (or taxing the difference).