Wow, I really like that theory Timo
. Makes perfect sense and it gives First Contact a lot more dept.
Using your theory we could also assume the first cube that was send in BoBW was an incentive for the Federation to start developing anti-Borg countermeasures: Defiant class, quantum torpedoes etc.
Taking it even further we could say "Endgame" too was a whole setup to allow Voyager to take back all that future technology although it seems kinda excessive for the Borg since it ended with their entire Unicomplex and transwarp network being destroyed. But heck if the tech is worth it to the Collective, who knows.