I have a Janome 6600. I have quilted many different sizes. I have done a queen but did not like it. I was fine with kid ones and large lap (55 x 72 or so). My desire to get more prolific lead me to an older HQ16--no stitch regulator and certainly no computer stuff.
I would think a machine like the Janome would work well for you. I did lots of walking foot quilting with it. I love how easy it is to put on binding totally by machine. I really love the machine. Not sure how big the harp is but I think it works very well and is one of the larger ones I believe.
I would think if you did the smaller sizes on your sewing machine and then sent out any of the bigger ones might work well. The main thing is to get back to loving the process.