You also definitely can't now find a Flood Weapon Editor on that thread either, and you can't make your own variant where the zombies have a primary and secondary weapon of your choosing. You cannot then upload it onto a flash drive using Horizon and put it onto your Xbox 360. But on the bright side, you can wait an undetermined amount of time until 343 decides to gives us such options.
Assuming they make it a launch title. I think they learned from Halo 3 that you can launch a killer game a year later and consoles will still sell. I'm predicting Xbox 720 in 2013 and Halo 5 in 2014. They'll probably release an expansion or "Halo Wars" esc game as their yearly sale point.
You are assuming 343 is going to give us that option in the future. I don't think they will because they will have to release another model of the Flood without the sword for a right hand which I highly doubt they will do just to please people who already bought the game. I could however see a "classic infection" gametype being added, where there is no flood character model at all. Which I think sucks because the flood look really cool.
Starship. I assume the easiest thing for 343 would be to release an Infection gametype aswell with standard spartan models. It wouldn't be used for matchmaking so I doubt they'd make the effort of remaking more flood models.
I'm not assuming they're going to give us that option, which is why I will use the Flood weapon editor I was talking about, along with other gametype mods, because I don't want to wait an undetermined amount of time until 343 adds in features that should have been in the game day 1.