My RV traveling machine is a Viking Opal 650. It doesn’t have everything you wanted (not mechanical, weighs more than 15 pounds, no knee lift), but it is very versatile. I do some home dec and garments in addition to piecing while we travel, and it does it all. It is much easier to move around than my BERNINA 440, and it sews a lovely stitch. Oh, and I got it on a great sale for $699 last summer. It lives in my motorhome along with a box of supplies. I store it all under the bed. I also have a Gidget table with a custom insert for it. I injured my shoulder years ago, and I need a lower surface to sew on than the dinette.