I agree, you need a good swing arm zigzag and the freearm is hard to live with out. There's all kinds of feet for the old Berninas, just make sure it's the old type (I think some of the current produciton models still use them, but I'm not sure). The Swiss zigzagger for the straight stitchers is the best, but I mostly use it as a walking foot, as a zigzagger it's a bit more cumbersome. There are even feed feet for the vintage Berninas, but they tend to be expensive.
I have not quilted much on my Bernina 730, or much free motion in general, but it does it fine. It has the same tensioner and bobbin case-race-hook as your minimatic. The tension is rather forgiving on these models, but as you know much better than me; you need the right needle and a good thread for the job. My focus was mostly on even hand movements and steady speed. I'm not sure the limits of layes and batting, but I think it has much the same foot lift as the old Singers. A 201 in a cabinet is ideal for larger quilts though, the flat bed makes it a joy to work on. The smaller minimatic has it's limits regarding harp space.