Kristen Alderson was involved with Chad Duell (Michael) in real life, so she might not want to reprise Starr Manning on GH, since it was not an amicable breakup. The two main things "GH Todd" was known for was 1) his almost-marriage to Carly, and 2) his original ownership of what became Aurora, the publishing company. When ABC forced GH to write out the OLTL characters, Todd just sort of vanished, leaving Connie Falconeri to run it. You may recall a mystery man named Derek Wells bought the company. Wells was actually Julian Jerome, and when Connie figured it out, Ava killed her. Derek Wells Publishing became Aurora, which Sam now co-owns with Jax. Todd could, in theory, swoop in to re-purchase his company--and become Sam's new love interest if the writers want our heads to explode.
I'm not really fond of them bringing Todd back anyway, since I will never approve of any plot point that would give Carly even more screen time. I'm just worried they will do something similar to when they resurrected Franco for him to play. If it's a new character, I thought he might make a good Cassadine cousin or even a long-lost relative of the Westbourne/Obrecht/Reeves ladies. Some have suggested he'd be back-from-the-dead Drew, but another facial reconstruction?* For a bit of creepy, they could cast him as freshly-released-from-prison Steven Lars, last played by Scott Reeves. Having him play Liz's brother rather than husband would be odd, but at least he would have reason to continue playing scenes not only with her but with the boys and Scotty Baldwin and a possibly-recast Heather (live from Pentonville!).
(I know recasting Heather is a longshot, but they have been working Heather's name into things recently, and it would make sense that she would be interacting with fellow nutcase Ryan Chamberlain in prison. Now with her dear son Franco dead, she'd have a reason to start breaking out of P'ville and causing trouble again. The way Robin Mattson has seemingly dropped off the face of the earth says to me that she must not be in good health, so bringing the character back would probably necessitate a recast. I think Kim Zimmer would be hilarious in the part, and just the sort of stunt-cast they'd attempt.
* Drew returns looking like Franco, though he hides his face until he can get Peter alone. Drew approaches Peter on a balcony at the MetroCourt. Peter sees him and, believing it's Franco back from the dead, totally freaks out. He begs forgiveness and blathers on about all the evil things he did, then falls off the balcony to his death when Drew steps toward him. Drew would have the confession(s) on tape, and security cameras would confirm that Drew did not push Peter off. It's a bit like Chip's death scene on Knots Landing when he saw Ciji's lookalike, but it gets rid of Peter at long last and perhaps establishes that Drew is not the same nice guy who went down in that plane.