I feel pretty good about this list. I divided the active characters up into main and supporting roles. There are some entries there that would initially look like a surprise until you consider how their roles have dwindled over the last 1-2 years.
I had to leave a lot of major names out to get it to exactly thirty-three characters but that's probably because my definition of 'active' main or supporting characters might be different from Jeph's. He might, for example, see Jeremy, Mrs Augustus and Punchbot more as 'set dressing', a character who will always appear in a certain scenario but has no role outside of that. No matter how hard I try, I can't get the list below 36 members.
I left out characters whose role, no matter how major, was limited to one or two arcs and never reoccurred, even when events suggested that they could. Examples of these 'one-off majors' are Faye's mother and sister, Lt Porter, Arthur the Support Group Moderator, Marten's dad, Henry and Delilah, Marten's one-night stand.
Active - Main
Faye
Bubbles
Brun
Renee
Elliott
Clinton
Hannelore
Winslow
Momo
May
Active - Supporting
Emily
Dora
Marten
Claire
Pintsize
Jim
Sam
Veronica
Punchbot
Spookybot - at jwhouk's suggestion
Roko
Inactive/Retired
Angus
Tai
Penelope
Wil
Steve
Cossette
Sven
Marigold
Dale
Steve
Beatrice
John
Raven
Sam Bean may move from 'supporting' to 'main' if her role at Union Robotics sticks and grows in later arcs.
[EDIT]
So, with that last edit, I've reached exactly 33 on this list. I'm not 100% with it as it stands as I've had to shoulder several characters into the 'Minor/Context-Specific' category that I'm not entirely happy with having there. Nonetheless, I think my list is reasonably workable.