You have a few options here. One, you can modify. I would simply add a keeping room to the left side of the house where the kitchen is. If you want to modify, we can contact the designers and get a quote for you. Two, you can find another plan that meets your needs. You won't be able to find a keeping room on a house that is under 2,500 sq. ft. living space. In fact, the smallest house I could find with a keeping, or a hearth, room is NDG-572. Here's a link: http://www.theplancollection.com/house-plans/home-plan-3409. This happens to be very similar to the NDG-983, so you might like it. Every other keeping room you'll find will most likely be on a house that is 3,000 plus sq. feet. living space. In fact, when you modify NDG-983, you'll probably be adding about 200 sq. ft. to that house. All things considered, don't be afraid of modifications. Even though a bigger plan will cost less if you dont' have to modify it, you'll spend way more when you build it. It's smarter to spend more on design and less on construction. The end price tag is much less. Even if you spent a thousand or more on modifications, it still would be much cheaper to modify and build smaller. So you can't go wrong by staying small.
Let me know if you have any questions. Contact me by phone to discuss your modification.