Hmm, that sounds awesome.

Imagine yourself in a situation, where there's plenty of melees available to party, but not a single healer. One could switch to healer, so party leader could pick up any of the available melees, and you'd have a full, balanced party. After the party, you could just allocate the xp you gained to that melee job, you were going to play in the first place.

Then again, in the end, there's a chance, like you said, that ppl would stick with their one or few lvl50 job/s, grinding raptors all day long and allocating that xp to another job, thus "never learning to play that class properly". Not to mention intense end-game content, that requires job-experienced ppl with good-geared characters. That... might be bad for the mid-lvl party forming too.

Maybe if they'd somehow limit the exp you could allocate per week? Or... Made it impossible for a capped job to reallocate xp? Maybe you could only transfer xp between certain groups of jobs, like mages < mages, tanks < tanks and cc melee's, dd's < dd's etc.

But yes, that does sound awesome.