I see what you mean about the touch switches and cuing. I don't have fingerlifts on my Magnepan tonearms and use the front corner of the headshell? to move the arm while resting my hand on the plinth. Touch switches would not work for this. The 500 had a slide switch, hit it one way to stop the platter and move the arm, slide the other way to start the record as the cuing descents.
Interesting 625. The arm from the 650 is one that I have had to work on. The race for the ball bearings used in the bearing got worn and the balls cut a slight groove in the race (top part of the arm tube) and I needed to pull that apart and sand down the race to fresh, smooth, ungrooved metal without the dents that caused the arm to skip 2/3rds of the way across the album. Don't know if this is a problem with more than one arm, could have been just over tightening on initial install.
That arm, I thought it had a 5-pin DIN connector but I don't recall for sure. Redoing whatever that is in the pic shouldn't be too hard and should provide positive benefits.
I can't see how much work the dust cover will be.
I'm refreshing a PS-2251 for a friend and to make it right is a lot of time. Hard to determine how far to go when time it money, but the results can be excellent with tables of this caliber. Looking forward to the results pics of this project.