That’s an interesting idea. How do personalities work? Do you level them just like another toon?
Personas are new classes your character can become, is essentially it. My main character is a tank, and he goes around with a main group. Any skill and spells they all provide each other is what I have. I can buy a persona slot and add that on main tank, so lets say I add 3 slots of personas. Main tank can transform into a mage, a enc, a rog, or back to his normal tank self. My main is 125, when I create the persona, each is a level 1. Instead of logging off to another character on the same account, I can now log onto one of my personas. Persona use the same banks, have your AAs Tradeskills, gear that your main has. My new level 1 mage persona is still RedFrog name, same as tank, the other classes will be the same. I am always still me 'RedFrog', even though I have switched classes. Many achievements and collections all completed by my tank, carry over to the new mage persona. The mage must be leveled like any character or can have a Heroic applied. This manner seems a little easier than logging off to another character on the account, if I have no trade twink things that the new mage can use, he has access to everything in the banks, keyrings, currency. So mount up the LS mount and level 1 mage can get the buff, etc.
The peronsa mage can (once leveled up) come CoTH or buff group, etc. But cannot park nearby to help easily. That is a difference from a normal 2nd character. The use is a little different, but workable. For example to help corpse run, a Persona cleric or necro cannot park nearby and log on to rez, but they can log on and use the campfire, remember its still 'RedFrog' so RedFrog the tank is in the fellowship, so is the mage persona, its not a different character.
If you bought or will buy LS, it came with 3 persona slots for the basic expansion purchase. There are good and bad things about the personas. I don't have much use for them myself, but it is a way they decided to go and does have some nice things.