Magento typical configurable product with multiple attributes goes like this:
For example there are T-shirts with different size and color. Each simple product has a size and color and then you create configurable product. That's simple.
But we need to create a product that is made of 2 different simple products that have different attribute sets. One has color and one size. It's a tent that is made of frame that has 2 different sizes and from cover material that has 2 different colors.
If you buy a tent then you must pick one frame and one cover material + you can pick some extras like sidewalls and carrybag.