Right, because there's no reason why the Scouts would mind being reliant on the Navy for their long-distance communication.At which point, they probably make use of the standing navy J6 runs... Or use the same plans the Navy does for the Fleet Courier.
I'd say that it was entirely plausible -- no, practically inevitable -- that the Scouts would TRY to get their own J6 couriers. How many they would manage to get would depend on how successful they'd be with their budget requests. They might or might not get to design their own version; that would likewise be a political matter.
Why would they use anything other than the X-boats along the X-boat net unless it was faster? Oh, right! A J4 courier would be faster than the X-boat net as we know it.For the most part, they're going to make do with J1-J2 to/from the X-boat net, and J3-J4 along it.
Hans