This is an update from Grey, the writer of Nightwing.
I have been informed by Crim (the writer of Titans) that he is dropping the project, hence the lack of updates. I have very little Titans information, or else I'd release all of it that I could for you guys. I guess we'll see if Crim decides to or not, I know his story bible is up to season 3 or 4.
What I do know is that Tim Drake would have come in as Red X (I sacrificed using Red X in Nightwing season 2, go to Nightwing for more information), Nightwing was going to cross over into Titans at episode 13 (and Barbara was going to cross to Nightwing in Nightwing 13), and Dick would have had a quick thing with Thea. What that was, no idea, we didn't get to it obviously.
Deathstroke and HIVE were the main villains, I remember that much. Raven may have come over eventually (she was only in Nightwing to let her exist for the time until she was ready to appear as a Titan), and I think Trigon was going to happen (Hence the "Seed of Trigon" thing in Nightwing).
Really the only other things of relevance I know is that I was only doing three seasons of Nightwing, and then Nightwing would have joined the Titans team (please see the Nightwing page). I'd have guest-written some episodes at that point.
A minor thing would have also been setting up some villains for the Suicide Squad (they were to appear in Nightwing season 3), and Thea was going to join them. I want to say it involved her having feelings for Grant, Grant dying, and then she becomes a comic-Deadshot-type character, someone who's willing to stay in the team. I think her HIV story would have come up (as per MiaDearden).
I apologize, and I wish this would have continued, I really do.