I'd like the part of the system which is used by ArchAge. They have 10 base attributes which can be combined. They'll have like 120 different jobs with different skill combinations. If that works with FFXIV is another thing.. but I can imagine that there will be some sort of advancing. Maybe a three level advancing? GLD > PLD > (insert uber jobname here). Like it'll need LV50 GLD to unlock PLD and then you have to level PLD from 1 to 50 and so on...

Leveling the PLD from 1 to 50 would assure that you learn/buy new skills during that time. I wouldn't like it if you could unlock a "title" and get new skills for that. So as Lvl 50 GLD you can be a LV50 PLD right away.

Maybe they can still work around the affinity stuff. Lets say you have level'd GLD, MRD and ARC. Combining a mixture out of those skill pools determine the new job and unlock better/newer skills.
At the moment we really have to be patient once again until more information are hitting us. ;(

P.S. I want my Blue Mage back :3 Hmm THM + PGL = Blue Mage!??!?!