I love the idea of packaged products. Why? Cause I'm a consultant specializing in high end development and design, and I've seen all too often people say something like "we love what you offer but cannot afford it right now", which makes me offer less value options which in turn takes more time and lower ROI for me.
The one thing I'd worry about is collecting client information for customizations. I spend a lot of time with my clients getting to know them, their business and their dog if I have to (and if it's not one of those "ZOMG it's going to rip my face off" types).
From what your telling me so far, you're going for the client that knows what they want right? As you've probably experienced before, not every client knows what they want so asking for 'some' information is great. The rest you might have to still call them and work out the details.
Which brings me to the final point: if someone doesn't fill in enough information, I'd have 'something' ready ... some process, company protocol, some systematic way to handle way to handle a lack of information and a way to handle an unhappy client.
Experience speaking here, you as the professional are responsible for getting the correct information out of the client, not them.
Other than that, you've got a great idea there mate.
Quick note on traffic generation: unless you are providing traffic generating services as an option ... it's not your place to worry about it. They ordered a product (the site + design) and that's what they got.