Size isn't the issue with loitering time.
This guy stuffed extra 2170s into his RC plane and flew 10+ hours. It's closer to the length of a Switchblade 600 but the (pre-battery) weight of a 300. And his plane is a behemoth compared to the
Nano Goblin which can fly over an hour out of the box despite a very inefficient wing shape.
The Ukrainian spokesguy who said Phoenix Ghost could loiter 6 hours also said it could fit in a backpack and take out light armor. That describes the 300. The 600 is (kinda) man portable but certainly doesn't fit in a backpack. And it can take out a tank.
What would it take to for a 300 to loiter 6 hours? I'd lengthen the front wing and add 1 kg of zinc-air batteries in the nose. Easy. At least in terms of flying. Getting a longer wing to fit in a 300's tube and deploy upon launch would be tricky, but give me a juicy DoD contract and I'd figure it out
Note the dates of the
Tacit Rainbow program.
Ground launch is easier than air launch, you just lose range. Here's a
containerized launcher for a recent AGM-88 variant called AARGM.