I do have a sitdown longarm. It doesnt have a stitch regulator, but i do have needle up/down as an accessory i requested when i ordered my machine. My machine does not have feed dogs.
I love FMQ and am now learning to work with rulers.
Just my thoughts, but i am thinking if there ever came a time that i wanted a computerized setup that i would probably just sell my sitdown machine and get a completely computerized standup longarm system? I really dont have room for a full blown longarm setup - which would also certainly cost more than the base price of $4,600.00 i paid for my sitdown machine (before adding accessories, supplies, and a saddle stool).
My understanding regarding installing a stitch regulator on a sitdown longarm is that if you have already been successfully doing FMQ prior to getting the regulator you might not like it at all. I am told in that circumstance - where you have already developed a feel and timing for FMQ - that the addition of a stitch regulator may well feel awkward and frustrating. As i said, i dont have one, but i think i can understand not being happy with one if you have already learned to quilt without it?
I am probably not understanding the question, so i apologize right off the bat for that! But with sitdown machines you move the quilt - not the machine. So other than maybe needle up/down or possibly a stitch regulator if that is your preference, i am not sure of the further benefit of a computer. I am totally willing to admit that maybe i just might need to be enlightened cuz i certainly dont know everything!
My goal with a sitdown longarm was to get more height and depth in the harp and to have the machine facing me. I had been doing FMQ on my domestic home sewing machine for years and was totally frustrated with the lack of harp space. I also really didnt want to keep abusing my sewing machine for fear of pushing it beyond its intended limits!