I see 0 issues with the interaction between red and green zones, if a green zone wants to put up a continuous effective front against a red zone clan then they have to become a red zone clan, if not then they can only raid and raiding will be useless outside of JH.
So if the devs make JH only a short duration then its going to be pretty boring anyway for them, this is where the short JH works against red zoners, because they can't defend themselves against people coming in locally and setting up raiding bases.
Basically by the devs forcing the red zones to be lesser pvp zones they put them at risk of being overcome by lesser pvp'ers
If JH was the majority of the day, or if you could destroy T1's for the majority of the day, there is no way an enemy can setup right next to your base and build a raiding base that they can defend from but you can't destroy till JH, you could say it brings more pvp but it goes to the group who has the larger numbers rather than the group with the smarter fighting sense.