I've said before what I don't like about it. But I'm still going to watch it and still have some hope for it.
I've been following 2 Supergirl Podcasts. Supergirl Radio and Supergirl TV Talk.
On this Alex character who is a foster Sister of Kara/Linda. I think it's possible she too is only adopted by the Danvers and that we may eventually learn she is either a sister, niece or daughter of Lex Luthor. There are a few characters from the Comics that could make a reference to, Lena Thorul, the daughter of Lex named Lena who became a sort of female Brianiac for the Our Worlds at War story-line. As well as Nasthalthia Luthor.
About the Superman being cast for the Pilot, he's essentially just a Stunt Double. Most people are thinking Superman leaves Earth in the pilot for some mission. While there is Comic precedent for that, in Live Action it'll seem too much like SR and it's horrible implications.
I think he'll die before the story starts. Killed in battle with Doomsday.
Casting an African American actor for Hank Henshaw means they are probably not going with making him Zor-El, which was a stupid idea anyway. So I can only think having him on the show alludes to his most significant contribution to Superman history, becoming in the future the Cyborg Superman.
Some people hate casting him as Black because of the Cyborg Superman aspect. Hank in the Comics did not look like Superman originally anyway. If the Cyborg Superman shows up in like Season 2 or something, he'll be a different actor physically, with this actor's voice returning only once it's revealed (to the non Comic reading audience) that he's Hank.
Other DC characters I hope show up down the line.
Metorpolis Police Detective Maggie Sawyer. She's DC's original Lesbian Cop, but Renee Montoya eventually overshadowed her. Gotham has mishandled Montoya so far, so this could be DC's second chance to do one of their notable Lesbian characters justice in a Live Action adaptation.
Livewire, one of the more interesting Female Villains of Superman's rouges gallery. And she has a History with Supergirl.
I'd like there to be a Cat named Streaky and a Horse named comet. But no Superpowers.
Down the line, like Season 3 at the soonest, I'd like to see a take on Powergirl, but it'd be difficult to decide what origin story to go with.
I do not know whether for sake of Adaptation Slam Bradley would be considered a Batman character because of his ties to Detective Comics, or a Superman one because of being created by Siegel and Shuster. But I want to see him on either this or Gotham, he's technically DC's original main character, he deserves a Live Action incarnation.