Confirmed Characters:
Dee Bradley Baker as The Bad Batch, CC-2224 "Cody", CT-7567 "Rex"
Michelle Ang as Omega
Noshir Dalal as Rampart
Rhea Perlman as Cid
Wanda Sykes as Phee Genoa
Mas Amedda
Tawni Ames
Gungi
Bail Organa
Rampart
RC-1262 "Scorch"
Darth Sidious
Likely Characters:
Dee Bradley Baker as Clone Troopers (Howzer, CC-3636 "Wolffe", CC-5576 "Gregor", Cut Lawquene, CC-1010 "Fox", CT-6116 "Kix", ARC-77 "Fordo", CT-5052 "Bly" Delta Squad (RC-1138 "Boss", RC-1140 "Fixer", and RC-1207 "Zev"))
Ben Diskin as AZI-3
Gwendoline Yeo as Nala Se
Greg Cipes as Zatt
Jeff Fischer as Petro
Olivia Hack as Katooni
Dee Bradley Baker as Byph
Georgina Cordova as Ganodi
Unlikely Characters:
Bob Bergen as Lama Su
Darth Vader
Ashley Eckstein as Ahsoka Tano
Al Rodrigo as Quinlan Vos
Dryden Vos
Sam Wither as Maul
Katee Sackhoff as Bo-Katan Kryze
Freddie Prinze Jr. as Caleb Dume
Likely/Unlikely Characters:
Daniel Logan as Boba Fett and Clone Cadets
Corey Burton as Cad Bane
Ming-Na Wen as Fennec Shand
Jim Cummings as Hondo Ohnaka
Tom Kane as Yularen
What other characters that I have or haven't mentioned could show up in Bad Batch Season 2?