We love Brown Derby for lunch. For lunch at Brown Derby, two of our boys ordered kids' meals, our oldest ordered an appetizer as his entree and my husband and I ordered appetizers and shared the cobb salad. If you are not on the dining plan (meaning you would need 2 TS credits) this is a great option for lunch. But I'm biased - it's my favorite restaurant at WDW.
We've also been to Mama Melrose, 50's and Sci-Fi. I won't go into detail about 50's, since OP is looking for something new, but we loved the food and it was really fun.
Sci-Fi is OK. Our boys loved it the first time, and the burgers/shakes were good. Since then, we've thought it was fine and we'll go again next trip. So it's not off the list, but not a priority. If you have never been there, it's a fun lunch.
We enjoyed Mama Melrose for dinner, but have not really considered it for lunch because it's pretty heavy Italian - but you could probably do the same as we do at Brown Derby - order flatbreads, etc.