There's really not an enormous difference between the DE-2 and DE-3(HP)finders. I have both and really don't have preference for the DE-3. There is often a considerable difference in price, though, between an F3 and F3HP based solely on the finder. The DE-3(HP) finder has slightly less magnification(.75x) vs .80 on the DE-2. If you can find a clean F3+DE-2, buy it.
The F3+MD4 is truly brick-like and not light. It was the 80s PJ's rig. There's really no convenient way to rig a vertical shutter release on the MD-4 outside the wart-like MR-3. Camera and drive can also be used for self-defence.