I don't know why you couldn't use a large trash can, or a barrel to do the same, rather than messing around with bags.
Silos aren't oxygen free, they just reduce the surface area exposed to oxygen because it is all stacked vertically. Same principle applies in a can or barrel.
Additionally, the gases that are created while it ferments, especially in the first week or so are EXTREMELY toxic, I wouldn't want bags of silage, of any size, possibly leaking those gases into a building or coop.