Thank you for your insight, Zyeriis. RMT did come across my mind when suggesting this, but I think some countermeasures could be put in place. For example, perhaps to ensure that both accounts are owned by the same individual, they must both be paid with the same credit card? Or even better (if it is possible), you can only transfer characters to accounts linked under the same Square Enix ID and you would pay for your services through your Square Enix account? Just some thoughts.
However, like you said, as long as I get to play on my 2 characters that are currently under the same account, it doesn't matter how its done. I think it could be a good business move too because of 1.) fees for using the transferring service, 2.) the character's monthly fee effectively went from $1.00 a month on the old account to $12.95 on the new account, 3.) selling additional Content ID's (expansions, etc) for the new account and 4.) satisfied costumers.
Ravenmore, at first I thought expansions and add-ons would be an issue... but we are still able to guest login on a machine that does not have any expansions or add-on content installed. The content (areas, etc) is simply off limits. Perhaps a similar approach can be taken on accounts that a character that is being transferred is put on to. All progress in expansion related missions and quests is kept, but you are not allowed to enter any areas until appropriate Content ID's are purchased.