If any character doesn't want to be with the group, they should create a different character.

I can relate to this thought process, but especially when starting a whole campaign (not a one shot), I like to show my players that I have some chops to build a real story and not just Mission to Mission. I think finding ways to motivate characters with the story is generally better than forcing. For one shots, you are all a group, deal with it.

The whole Decker thing has changed a lot. I tend to push them in with the rest of the team. Older editions really had it so your decker was the guy back at base providing remote support. There's a lot of good incentive for them to join the rest of the crew on location.