We had a post on it before but I didn't want to bring that one up by replying to it.
The last time this was mentioned I believe it was decided that the Americans didn't need an AA vehicle when they didn't have a map with planes.
Operation Cobra needs movable AA defences for the Americans. I can't fly, and after being shot out of my m10 enough times in a game I want to hop into this:
I then want to drive over from the American main and gun down those anoying planes.
The Germans have got two AA opel blitzs on that map. We shouldn't have to use those to down enemy fighters. USA is also the only major side without an AA vehicle.
I mean we have the halftrack. We have the .50 cal. Not too much more to do the other stuff.
This vehicle would also be useful for infantry support (the biggest role of this vehicle anyway due to lack of german air power). Just give it a maximum seating of maybe 2-3 people so it can't be used like a halftrack.
As a side note I think there are many more halftrack variants for both the USA and Germany which could be quick and easy additions compared to entire new vehicles.