Just a quick update on my previous post with this problem.
I eventually managed to get all of the accounts setup fine, however, every damn one of them got suspended in the process. I found a way around that though.
As long as you setup the POP3 import and leave the box UNCHECKED for “leave a copy of retrieved messages on the server”, you will then receive a email on your previous email system indicating that the account is suspended, and most importantly, some directions to appeal this decision.
After having a human at Gmail manually unsuspend the first two problem accounts for me (roughly 8 hours after submitting the appeal), the other 4 accounts were automatically unsuspended as soon as I submitted the appeal request which allowed me to continue setting up the accounts.
So from what I have learned here, the reason for suspension is completely unknown but is NOT for breach of terms and conditions (which I have thoroughly read every single word to make sure), And if this is happening to several different accounts, once the first couple are reviewed by staff at Google, I guess they whitelist your IP address or similar to have the others automatically resolved when you appeal it.