I thought I had responded, but apparently never submitted it.
Credentialing can be a bear, there is really no way around it. With a new group you will have a new Tax ID number (TIN) and need a group NPI as well as the individual NPIs.
Some issues will depend on your Practice Management system. Each has a different way of changing NPIs and TINs. Usually takes weeks to months to accomplish the transition
If your provider is starting before the group is finalized, you might have to do this twice. So it might be better to have them start under the new TIN and add everyone else as you progress.
As for AC and changing the name, I'm sure they can do that, you'll need to talk to them. Of course, an additional provider with be an additional expense.