If you want to know what units are planned for LI, have a look at the HH 2.0 28mm black books as the core units in there lend themselves to down scaling ;)
I picked up two of the Malcador boxes and one of each support box. Despite my best efforts, I couldn't snag the cards. I almost wasn't able to get the book, but lucked out at an independent.
I'm not sure about Heresy-era Leviathan characters but Carab Culln, chapter master of the Red Scorpions, was interred in a Leviathan sarcophagus and actually got a Forge World model (now out of production) which might be an interesting project if you ever fancy doing a litbash for the era Indomitus
Didn't pick up anything yet, short on money so keeping it stashed away for the inevitable "surprise here's the titan and knight boxes give us a million bucks with one weeks warning" announcement. From the book, I'm kind of annoyed they showed off the names for those solar aux regiments to match the decals, but no paint jobs! I want canon paint jobs...
Sadly the print quality of the book cover is an absolute embarrassment, since GW didn't bother using an image in a sensible print resolution. One can spot individual pixels a mile away. Anyone else with the same issue? I expect the entire first print run to be affected.