CptTrips - dare I ask anything further on this? 
Well, let me back up to first principals a second.
The original reason I did WW1WF and was considering a WWII version, was to find a way of making the AI capabilities of AH more accessible to the average AH player.
* At the time, offline missions were mostly broken.
* Online missions via a Custom Arena were confusing and awkward for players to run. It was just too much friction.
* The Mission Arena also had awkward, confusing workflow, with the additional draw back of a lot of waiting around for schedule missions to start. You could end up waiting around 10 minutes for a mission to start that would only run a max of 15 minutes. Often way less than that. And there would be a lot of waiting around for the next scheduled run. The only way I could see that working is if the mission were very large scale and maybe 1hr long. A player could die and go to the Populate dialog and respawn into a different aircraft already in flight. The scale and duration would have had to be sufficient to justify the friction and overhead. Still, I think the UI workflow would have been too confusing for the average player. It's easier for them to just click on the Melee button if you make anything too much effort.
So I thought the persistent 24/7 AI augmented arena was a way to provide AI targets to the average AH player with the minimum of friction. There would be no waiting, no complex UI workflow. The player would interact with the arena exactly like they do the Melee. They simply launch at will from a field and fly to the action. It is a workflow they already have memorized.

So to your question, I had about 70% of my terrain completed and was starting some initial prototype missions, but then found out about the complete rework of the Offline Mission System Hitech was doing. I put the WWII arena on hold to make him a set of 64 offline 4x4 dogfight missions so he'd have a good library of content to show off when he launched the new features.
While doing that, I became impressed enough with the improvements to the Offline UI workflow that I realized he had solved the problem I was trying to solve with the AI arena. It can't be easier now for a player to select an Offline Mission from a nice list and immediately launch it. The new changes have made missions very convenient and approachable now.
When I started the planning for the WWII AI arena, I didn't know this was coming. At this point, I think the Offline Mission system might have made the need for a AI augmented arena obsolete. Building an arena is a metric crap ton of effort. I'm having a hard time seeing what the benefit would be at this point vs a set of individual Offline Missions that would be a lot less effort and could be done incrementally over time.
So currently I'm not working on it. I'm feeling like there is no longer a good justification for the amount of work. I've even suggested Hitech close out the WW1WF arena and I'll just convert those to offline missions.

[Edit] I had toyed around with the idea of reducing the scope and only making a Pacific war arena. That could be used here, and maybe over in War Online: Pacific. Getting two uses out of the same work would almost make it worth it.