I actual disagree here too.
There's no reason free accounts should be limited at all under an ideal system.
The basic account should be the basic account, no restrictions, no limitations.
A subscription or premium account should offer advantages, logistical more than anything else.
Purely out of thin air;
Let's say paying $10 a month meant you could upload a custom guild logo that you could make into wearables, you would get prime NPC spots at banks for your own vendors, your runebooks became unlimited charge and you get special dye tubs that only paid players can use and insurance is free.
That right there is more than enough to make certain people want to pay, practically every current player would jump on it, because it makes no difference, they pay anyway right now.
when you then consider the micro transaction angle, you go all out, more character slots, extra bank space, special items, ridables, bless deeds. I'm sure others can come up with better ideas.
the trick is to maintain skill based balance, the player who's better at the skill based aspect of the game, regardless of account type should be superior in all competitive aspects of the game. Once you have that, the limit is your imagination.