A powerful tool in the early stages of developing scenarios is to pretend the interface is magic. If your persona has goals and the product has magical powers to meet them, how simple could the interaction be?
In the early stages of a project, it can be productive to imagine that the interface you’re going to build can do whatever you want it to do. I try not to think too much about ‘how are we going to achieve this’ because it limits the ideas we come up with.
A great idea might be achieved despite the limitations of the technology.
If you aim for 150%, but end up only reaching 125% because you have to rein in your ideas later in the project, that’s fine. But if you start with the technical constraints, you’ll be aiming for 100%, and the end result might come in at 90%.
BTW Not really relevant but writing this reminded me that the iPlayer volume control goes up to 11 : )