man that is the real problem with the entire power drive line of Minn Kota motors, (which I own and also sell, so im not bashing, just stating the obvious) . The design is...well...bad. You cant mount them without sticking out over the front of the boat a foot. Really MK? Comon!
I saw a couple of years ago the bracket you want in a Bass Pro or Cabelas mag and thought, NICE! THATS what I need. By the time I got around to being ready to order one, I couldnt find it. And still cant. It must not have worked well because I dont see them any more. The quick connects come in one that slides (like you mentioned) but only to take on and off, not to adjust back or forward. Somone needs to make one for sure.