Now I'm not sure if anyone on here knows who Sliding Ghost is from Bungie.net but yeah this all his work pretty much.
He found a way to bring the zealot from the refinery over towards the AA gun and then managed to get him in the gun, I tried it myself with a guest and it turns out the falcon will happily fly through the valley with the zealot in the gun but he wont be shooting those covies for you so you wont get his cover.
Only problem is the player used to get the Zealot in the gun is left behind leaving the falcons stopping halfway through the valley, I've thought of using 3 players and seeing if the guy used to get the zealot in the gun can get in the second falcon in time in the hope that the falcons will fly their path, however I'm quite restricted.
First I've got 3 controllers, but only 1 battery pack and 1 play and charge pack, I can't have all 3 on at the same time, I'd have to do it in co-op campaign to have 3 players of one console in one campaign game as well, to make it better I just got a new xbox and had to transfer a lot of stuff onto it but I've had problems loading campaign and multiplayer maps, before the new xbox transfer I tried it with a very good friend but huge amounts of lag stopped any attempt at doing it.
With these problems here I don't think I can do anymore as I've been working on this for quite a while but I've pretty much ran out of ideas and I'm not sure I can help at all as all I'd do is cause lag probably, with the help of some others this could finally be done with, don't have hope it'll be some huge discovery that will be a major hit and get huge amounts of activity, I wont be surprised if the zealot dies by a kill barrier or despawns before reaching the cutscene but it's something to try.