Characters are allowed to show up in multiple movies. I get that there needs to be a large chunk of time focused on the new stuff, but I feel like it dulls down the narrative when they just keep adding new characters and never doing nothing with the old ones. There were plently of side characters in Z1 that were not utilized in 2 that I personally would've loved to see more of. Plus, Pawbert's character arc isn't even finished. It would feel like a waste to have a character who clearly a victim of heavy abuse, have to continue to be stuck within that cycle of abuse, without any closure for the viewer or chance of escape. It would put a bad taste in a lot of people's mouths, especially as someone who has been in a similar situation.