Our mast is deck stepped with the wiring going down the compression post to the bilge area. I'm not sure how I'd get the wires out of the compression post above the bilge. They don't get disconnected very often, I can join them with butt splices that have a heat shrink covering, cover that assembly with shrink sleeve over the whole thing, then wrapped with self sealing tape. Tie the junction up as high as I can get it in the bilge. If Raymarine had their way, you'd disconnect it at the display and unstring the entire length out of the pulpit, and the bilge. I had to do that when I replaced the knotmeter transducer.
I guess I've been using the terms lazyjack and stackpack interchangeably, it's all one setup on mine. It's the foot of the stackpack that in is the boom slot for it's entire length. There is no opening in the botttom. So to remove it I have to completely slack or remove the lazyjack lines, get enough slack, then pull the stackpack out of the forward boom slot. Then I can bring the slug at the aft end of the sail forward and remove it from the boom.
You mentioned that your stackpack closed he foot with wire ties under the sail. I wish mine was like that.
Right now, since I can't figure a good location for enlarging the slot, my thought is put it back together as it was, wrestle the sail and stackpack into place, and once it's installed I can pick a spot and enlarge it later. The new standing rigging will be back from the rigging shop tomorrow, so they'll want to restep the mast fairly soon. I took it off by myself, and it was a bit of a circus. Newish, stiff sail, and the the stackpack isn't easy on it's own. The long piece at the foot that goes into the boom slot isn't flexible like the rope on the foot of a sail, and it has battens in the stackpack. So I have to get the mainsail slug in first and pulled aft, the feed the stackpack around the flopping sail and stuff it's length down the boom.
It's mostly really awkward to do by myself. My wife doesn't know it yet, but she is going to "volunteer' to come down to the boatyard and help. She can handle it and knows what she is doing. Back in her 20's, decades ago, she and her first husband built a Bristol Channel Cutter from scratch. Made the molds, laid up the foam core fiberglass, made the interior, made the spars, and she sewed the sails. She knows fiberglass, wood, paint, etc much more than I do. I'm the systems guy, I'll get it all to work. 43 years of turbine aircraft maintenance, I must have learned something!