I have made serger quilts before..baby sized but it is a lot of work to handle the layers for the quilt as you serge method. The sewing space to the right of the needle on sergers is much smaller than our regular sewing machines.
(Note to Bernina....next serger should have needle down button ..again..and more space to the right of the needle please!!!)
I do use my serger for the super scrappy tops. I will cut up scraps into 2 1/2" squares. I don't worry about color or grainline but I piece into blocks using my serger. I just use a 3 thread overlock with a stitch length of about 2.0 and used the edge of the serger foot (which for me is 1/4"...measure from your left needle to the cutting knife) for my seam allowance. As I put together the blocks (5 squares by 5 squares) I didn't worry about color, just lights and darks. I figured that the serger stabilized the grainline and if the color mixing was too horrid, I could overdye the blocks with a tea dye to tone down the colors. Having the serged edges would keep the blocks from raveling. There is a large quilt in my profile that I pieced in this method...a king size bedspread.
However, I quilted it traditionally on a mid-arm sitdown
kim