I think because Golovkin has a great chin and would be very respectful and cautious of Jacksons skill and power , as he was vs Lemieux and Jacobs, that he would first establish the jab to soften up Jackson. Then after GGG softens him up with the jab, and establishes timing and distance, look for GGG to take jackson out around round 10. I think the fight would look like a cross between the jacobs fight and the Lemieux fight.
I also fancy Golovkin here. JJ was a brutal puncher without doubt, but he really didn't have a very good set of fundamentals. Golovkin's fundamentals are top notch and he would very likely give JJ the respect due to him. I reckon he'd establish the jab, use distance to deflate Jackson's more loaded-up swings and dismantle him technically the same way he did with Lemieux. I reckon Golovkin wins by KO between tounds 6-10. Let's also not forget that GGG is the natural MW here and JJ is coming up in weight.
If Julian Jackson and Triple G fought each other 10 times. Jackson wins 3 . Triple G wins 7 . With that kind of Murderous Power , Yes even Iron chinned Golovkin can be clipped and put to sleep. This is a 50/50 fight. Gun to my head I would lean slightly towards Triple G.
GGG and Julian met each other with the hardest crosses they've threw in each others lifes, as GGG backs away, dazzed, dizzy, tripping over his own feet, going into a high guard to not recieve more punishment so the ref does not stop it, he realizes Julian is already in the floor being counted out.
This simplistic, almost child like analysis but in the battle of power punchers, back the guy with the better chin.