Well, what do you think this universe consist of? First you need to define conservation laws, and in which way they are valid. In a 'container model' conservation laws seems more appropriate than in a model where no limits exist, especially if we assume a 'energy' to this universe. Because if a vacuum has a 'energy' you will need to define what happens with it, as a SpaceTime geometry grow. Does it dilute with a expansion? If it stays the same, where does this balance come from? Locally defined any energy you ever measure comes from a interaction between mass and vacuum. So as you find a redshift you either define that from a container idea, in where we somehow, although define a universe as possibly limitless, yet expect it to become larger. Any idea, describing it this way, seems to me to assume a 'outside' from where it can be defined as expanding.