What changes would you like to see in 4th job skills?

Archmages: Remove ultimates and power up fire demon/ice demon/paralyze/chain lightning/big bang to allow archmages to train at a similar pace to other classes. In the ultimates' place, a new skill should be added that removes weapon/magic cancel but with quite a long cooldown. This lets them become more useful at bosses in a unique way.

Then the mage class will no longer be the gods of AoE. You'd have to up the damage of "fire demon/ice demon/paralyze/chain lightning/big bang" by a substantial amount. Also, Big Bang is almost like an ultimate with quartered range and neutral damage. Upping that would be contradicting your statement that Archmages are overpowered with their "ultimates" when you're simply taking one form away and replacing it with a different form, one arguably better because of it's lower mana cost.

Also, why would a mage even need that much (I believe they have 18K mp at level 19x) MP when they can't even use that much. Since they have around 2K-ish HP, they only need 8K mp for magic guard, what's the other 10K for? Nexon designed Meteo and Blizzard in a way that makes mages... different from other classes. Your changes make mages too similar to warriors in my opinion, and I assure you that if you up "fire demon/ice demon/paralyze/chain lightning/big bang" to the point where it's balanced, the other classes will complain about you being the best bossers because of versatility.

Bishops: Remove genesis and replace it with a forward piercing mob skill that allows them to train at a very slightly slower rate than others, to compensate for holy symbol, like what I'm proposing for paladins. Also, replace infinity with the flame wizard skill that converts the archmage's own elemental spells to neutral.

That's a good change, but then again, you'd have to make the piercing mob skill pretty strong because Bishops in a sense, are magicians, and magicians are always mobbers. Making the piercing mob skill strong means that you'd have to make the skill overpower a certain skill Marksmen have called "Pierce" and then you can say that Angel Ray will be useless because all the Bishops, if soloing, will use that as single target.