I actually conjecture that it's a calibration type thing; The people who can download need to be made after the hub is made, otherwise they won't sync or whatnot! Well, I actually have no basis for that statement except the conjecture that things are always 100x more complicated than they seem.
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I suspect the Hub has something to do with the group consciousness of the Cylons, ie the hub servers to store the memories of Cylons, while the Resurrection Ship serves simply to resurrect the body and copy the data over from the hub. Resurrection ships may have no ability to store memories to prevent iced Cylons from resurrecting - the mental essence would instead get sent to the hub and the iced Cylon wouldn't resurrect, allowing for centralized control over the Resurrection process and (theoretically) preventing rebellion.
What's interesting to me about the Hub is that it's relatively new - it's obviously of more recent Cylon design than the hybrid ship - and it also seems to imply that the Cylons are actually a space-based race. Otherwise you would expect that the Hub would be located on a planet simply because it was built there first.
What's also interesting is that it didn't have a backup FTL drive in that other little spire thing. One would think that the Cylons would, at some point, realize the value of backups on their backup ship. They didn't have one on the Resurrection ship either, and none of the Colonial ships appear to have one. Makes me wonder if the FTL drives cause some kind of interference or has immense standby power requirements that prevent them from being installed on a ship that already has one.