More than half of our ideas span more than one product. An example is localization in a certain language. The tool restricts you to choosing one product and enforces you to choose a product.
There is also the case that an idea IS a new product. That should not be associated with an existing product.
The tool is designed with a very linear execution process. Real life is not like that - more flexibility is required. A workaround was suggested by support and we are using it but it is far from ideal
There are a couple workarounds which can help your use case.
We recently launched a new feature: universal dependencies. This allows you to create a link between any record in Aha! You can read more about it here: http://blog.aha.io/universal-dependencies/
In the situation where your idea spans multiple products, you can create links across your multiple products.
In regards to the situation where the idea itself is a product -- this workaround is a bit more abstract. You can create a product called "New product ideas" and move all ideas/products into that product. You can then track them accordingly and add your new products when you are ready to start building.
We hope that the above workarounds can help. At this time, based on existing functionality and current priorities, we're unlikely to make additional updates but hope that this can help.