I personally do not think any form of "tiered" job system would be good for the game- as it asserts the combination of ROLE, JOB and CLASS into one package and thus forsakes the malleability of a non-tiered job system, where job and role are a matter of whim, and disciplines function to make jobs more playable. In this respect I think it would be silly to treat "job" as a funneling device, and while it worked fantastically for RO, it also crushed Ragnarok when Transcendent Jobs were added- effectively ending Ragnarok's golden age.

I am of the opinion, that a job system should create the permanence which the original design was afraid to put in- however instead of tiers jobs should share "families" which allow them to interact with one another. I would propose a 12 job system, with 3 families of 4 jobs- 4 permanent pieces of character development which are honed by armory skills and put through 4 jobs to allow the player to fully realize their character. After undertaking a job- the player may ONLY switch to jobs within the same family

Family A (Warriors)
Paladin/Templar
Dragoon
Soldier
Hunter

Family B (Ascetics)
Thief
Monk
Berserker
Geomancer/Devout

Family C (Casters)
Summoner
Sage
Dark Knight
Red Mage/Sorcerer

Just another twist on it I suppose....