I have no recommendation on a machine but one that does basic stitches and a decent harp space would be essential for me. My machine has a number of stitches available for use but the the ones I use most are the straight and zigzag, occasionally the blanket stitches for applique but I wish it had a serpentine stitch for "not so stitch in the ditch" quilting.
You mentioned making the weighted blankets. I've done that and recommend that you use a tightly woven fabric such as in a sheet and then a cover for that so that it can easily be laundered. Be careful that the pellets are out of the way when you begin filling the grid and stitching!