Daughter and I spent all afternoon browsing the internet looking for house plans we could use...since we are interested in passive solar, I finally googled that and 'en voila!' I found several plans that have daylight basements that can be slightly altered to give between 1000 and 1300 sq ft of toghetherness but seperate living area-
We especially like the one called Brighton
I know this site is run by a plan firm but frankly and sadly havn't seen anything to compare--so heres some ideas for your firm too!
http://www.sunplans.com/
is the url