The reason for the B account was originally to keep separate the booster and the low levels because A wont have a direct link to CDEF. But I guess that isn't necessary. However, I'm still going to do it that way because unfortunately I no longer have the CD keys for Account A and I just want to be secure.

As for what will happen with account A, nothing. As soon as I'm done boosting I'll just xfer my hunter to one of the slave accounts (so I will have a total of 4 hunters lvl 80) and then deactivate it.