Definitely baked beans on the side (I make Raichlen's scratch version----onion sauteed along with bacon, so it cooks in the bacon fat, plus cans of great northern or navy beans, plus molasses, maple syrup, worcestershire sauce, mustard powder, your favorite bbq sauce, jalapeno pepper, and maybe some other things I'm forgetting---delish!)
I like my brisket sliced, and my peeps demand that I leave the fat cap on cuz they LOVE that melt in yer mouth tasty fat once it's cooked. We reheat it by slicing it and nuking it for like 10 seconds, until it's glistening with grease. OR we'll eat it cold (or at room temp) with horseradish like you'd do with ham.
Wouldn't hurt to have cole slaw on the side---all bbq goes with slaw and beans.