Why do you need a workshop? Well, that is an odd question, the real question is why would you NOT want a workshop! They are great, they have a million uses. They give you so much room for activities!
This collection of home plans with workshops is the only collection you'll need. All the other features you could have, like a fireplace, mud room, media room, or even a rear porch all pale in comparison to having a workshop.
You might think you don't need a workshop, but you'd be wrong, dead wrong. When the day comes, and it will, that you wish you had a workshop you'll understand. In the future adding a workshop will be extremely expensive, and it will mess up your home for months. And in the end it will be a compromise between what you wanted, and what you could "fit" into your home. So, make the smart move and build your new home with a workshop from the get-go.