The Armoury System has to be the most limiting system there is. It's good in theory, being able to equip a weapon or tool and change into the job you like to be, but in practise it's absolutely horrible.
Please remove it entirely and make us change classes/jobs by means of an equippable crystal or simply letting us select them from a list (as we do with gear sets already anyhow).
Why? Because right now having the armoury system in place will mean that we will never be able to get unique weapons.
On my Paladin, as much as i like my sword and shield, i would never be able to equip a Great Sword if they ever were to think of one, or hold a Staff if i wanted my healing potency to be improved. Same for being on Warrior that you'd be stuck to having a Great Axe. If you were to make a Great Sword that's (GLD PLD MRD WAR) as far as classes go, simply equipping it will switch you into one of those jobs, it cannot be both, one will be defined as the designated job for it :/
Not to mention you're most likely going to run into problems implementing things you already have planned such as Thief in the first place. Gladiators might be able to use knives, but so do Paladin. This will make it so that you are unable to have a diffirent base class than Gladiator for Thief already due to the weapon choice, severely limiting any unique options it might have (you'd basicly get 5 new abilities) and have everything else that Gladiator (and thus Paladin) has as well in all the other slots.
Simply no longer having weapons be bound to specific classes and jobs through the armoury system will open up so much more options. Samurai for instance no longer have to branch off Lancers always having to use spears but instead can then hold Great Katana's. Since sticking to the armoury system would mean that either Lancers (or whatever base class you decide upon) will get access to Great Katana's too otherwise you wouldnt be able to use them on your advanced job as well. And thieves can have unique skills and not most of which you find on Gladiator as well.
It would also mean that "jobs" no longer will replace "classes", with them being mere upgrades with more skills available to them, but rather requirements for unlocking and/or alternatives to it. It would also mean you can get Gladiator to 30 to unlock Paladin (30), level your Paladin to 50. And have a totally unique Gladiator with many more skills to obtain for them to level from 30 to 50 as well. More time spend, people having more fun leveling, more uniqueness and many more classes to play in whatever roles they decide they want to have.
I'm not saying i know what you have planned as far as equipment goes, or even what you have planned as far as classes/jobs go, but i know sticking to the (archaic) Armoury System is going to severely limit and hinder any possibility of classes and jobs being unique and having access to more and diffirent kinds of weapons.