Some friends and I have been discussing the probability of reviving a dead spren, and came up with a theory, and a little short story for kicks and giggles (Sorry if it's terrible!)
Our theory is that a Bondsmith's (Dalinar) hidden ability is to Rebond "Dead" spren (Shardblades) to a worthy person, which restores their cognitive abilities, and forms a new Knight radiant.
The theory is partially brought to light by this passage:
So Melishi retired to his tent, and resolved to destroy the Voidbringers upon the next day, but that night did present a different stratagem, related to the unique abilities of the Bondsmiths; and being hurried, he could make no specific account of his process; it was related to the very nature of the Heralds and their divine duties, an attribute the Bondsmiths alone could address.
As well as to their name itself: "Bondsmith".
We know the bond that creates a Knight Radiant is called the "Nahel Bond".
With this in mind, and other discussions around the matter, we wholeheartedly belive that it is possible for a "Dead" Spren to be rebonded, restoring it.
We believe the process would occur as such: (Short story written to explain)
Dalinar and an Unknown wielder of a dead spren shard blade are sitting in Urithiru, in a dark room.
The unknown person (Probably a young lady, because... yeah) sitting there with the blade across their lap, eyes closed, and focusing. This goes on for days, as Dalinar trains them.
Dalinar: "In order for your bond to be forged, you must determine the nature of this spren, and align yourself to it. You will make changes that will alter the very way you live and think, but if you work hard, and are truly dedicated, I will grant you the bond, and repair that which has been severed. This blade, no, this Spren shall be your partner, and you will unite together to help save our world from the darkness that has arisen."
After a long while of training, they both begin hearing a heartbeat from inside the now glowing blade, and she (the wielder) begins to feel strange. She begins hearing a small broken voice repeating the same words in her head. "Honor...." "Strength..." "Courage..." "Devotion..." "Duty...". Suddenly Dalinar opens his eyes, and a burst of stormlight leaves him and enters into the meditating person, who opens their eyes, shining bright. Words spew from her mouth. "Life before death, strength before weakness, journey before destination" as the blade slowly disolves into mist, and begins reforming in the shape of a small, young woman in front of her newly glowing eyes. "Hello, I'm (some spren name), I've been calling out for so long... Thank you for hearing me!".
Dalinar stands, and places a hand on her shoulder, looking down at her. "Welcome, to the Knights Radiant. From henceforth you shall be a member of the order of Wind Runners, under your new leader, Kaladin Stormblessed. Congratulations, young one." He turns and smiles, and introduces himself to the Newly resurrected spren, Then leaves the room to allow them to become better aquainted.
So... yeah! Hope you enjoyed our theory, and short story.
Please proceed to tear it to shreds if we overlooked something!