Are you building the space or do you have the space but trying to figure out if everying thing will fit?
That long arm alone is going to take up a lot of space. I would make sure that you allow a minimum of 36" around its' perimeter for space to walk around it. So...if the long arm machine is 12' long then add 6 additional to the length of the room . Width of the long arm plus 6 feet.
I used to do space planning for commercial offices. 36" is the minimum space for foot traffic-movement.
sandy