Fusion could benefit enormously by adding in the functionality of symmetry planes and axes while creating symmetric sketches and bodies.
Rather than wasting time drawing only half a sketch for a symmetrical part, then having to mirror that, then do a combine/stitch or whatever to it, why not provide symmetry planes and axes to do all that for right from within the sketch!
I tend to be a whole picture guy so really don't like having to design something in halves, and then have to perform more functions to it just to get it to a whole. I want to actually see what I am designing as I'm designing it. Using symmetry axes and planes does that so simply and easily. I have used it in other software and I absolutely LOVE it! So fast and easy.