If your going with a JPac or IPac for your keyboard encoder (you ARE going with a keyboard encoder right?) Andy sells Trackballs for cheap... And yes you need a mounting kit for trackballs (some have got around it, but it will save SO much time...
Do go with quick disconnects... If you don't, you will make your cabling a real pain in the neck, and very very unforgiving if you have to take it apart for any reason. For these, you can get them from different places, but Pearle right here at this board (buy/sell/trade board) sells them for cheap.
Yes, you mentioned what does and does not need a mounting plate. The mspacman does. GREAT joystick. I have a wico but want to change... but its hard since the wico 4way leaf switch joysticks are pretty good themself... but not as good... and I was happy with my 4ways until I tried Oscars pacman cocktail table... DAMN YOU OSCAR!