Yeah, that's what I thought too - the dead spren could only be revived by the Radiant that they had the Nahel bond with? Correct me if I'm wrong though. Also remember how the spren react near the Shardblades - they scream to the point where the Radiants can no longer fight.
Basically, I think the Shardblades will be largely useless in the fight against Odium.
What about Eshonai though? For some reason, I thought that her being the first to take up the Stormform meant that she was Odium's champion? Or am I just speculating total nonsense oops