I've always assumed that the knowledge of the Collective is too vast to store in one single drone so that it is maintained in both computers and distributed over large numbers of drones - each drone knowing a (small) part, but with enough redundancy and distribution to ensure that no knowledge is ever lost. But perhaps I'm wrong in that assumption. Now, Regeneration. Only 2 drones are revived, and as far as we know they didn't take any computers or databases from their original craft with them (though that of course could have happened offscreen). So, how much technical knowledge did those 2 have? All the knowledge of the 24th century collective, or significantly less? Given time, could they have built a fully functional cube with all tech standard to the 24th century Borg?