ya I fully understand the thought process, though I don't think there is a need for a carry item for anything really because I think that it actually defeats the purpose of a jungler.
Imo jungle items should be complimentary to a playstyle, With FF there complimentary to a carry style, though FF in itself is not enough to carry a game with, but helps with bonus gold generation and infinite stacking mechanism. Additionaly, besides just raw stats golem and lizard lend themselves to there specific roles through tenacity, and the burn passive. Spectral wraith doesn't really have any special passive other than the crappy stacking mechanism, which lends itself to farming, which wouldn't really fit the role of a mage jungler.
But to be fair giving wraith a proper passive is hard because of the different types of ap characters. Obviously just giving it raw ap stats can work, but a lot of junglers that need scale with ap, don't actually prioritize ap, rather more so magic pen, or CDR, or even spell vamp on the S3 wraith is better than what it is now. At the start of the season it had a proper passive, but when it was shown the power of that passive it got toned down, moved to everything, and in return wraith got a much shitier passive that makes it worthless, actually killing mage junglers.
Sorry kinda went on a tangent off topic just realizing.