Yes, we have discussed this quite a bit. The general idea of requiring people to enter more details about their vehicle is something we think about quite a bit. As we've said before, we definitely will add manual vs. automatic. That is on the way.
Beyond that, we're comfortable with the details we ask for right now. We ask for fuel type, engine type, body style, and soon auto vs. manual transmission. There are potentially dozens of other attributes that can affect fuel economy that we could track. Drivetrain is one. Engine displacement is another. People have different ideas about what the bare minimum is. Some feel you need to ask for all of these and more. We feel like we don't want to alienate people by asking for too many details.
We'd rather see more data with fewer details, partly because we feel like having more people tracking means more people thinking about their fuel economy. Some people choose to include these details in their vehicle description, and that's great. We encourage people to do that, but we don't make it a requirement.
Here's the FAQ on this topic:
Why don't you track more vehicle details?