I am having a bit of trouble wrapping my head around their decision offer them stock ONLY with the P neck, but to sell J necks that can be purchased and installed by the buyer at his/her cost and risk. They should IMO offer them with either nec, from the factory.
No, this isn't a question of "I want them to offer MY custom option!" I understand they can only sell for low prices by having a stock set of features that all their machines are set up for. So, forget fret size, color, this or that option... it's not there and that's more than okay.
Here's the thing: they are already going to be manufacturing J necks that will fit the P7. So, in order to sell one that comes with a j neck installed, they won't need ANY additional machining or retooling; they will already be making these necks.
Why, then, won't they offer the bass with a neck they are already going to be making? Does it cost more to install a j neck than a P neck? No. All they need to do is have them at the factory where they are building these. Perhaps they will build the j necks somewhere far way, and would have to ship them to the manufacture location, whereas the P necks will be made onsite? Maybe. That's all I can come up with.