Something that's always interested me are how Genesis and Sephiroth are seemingly two sides of the same coin for Jenova's capabilities:
Jenova's Head: slitted pupils, white hair, glowing left eye.
Genesis' Head: Normal pupils, normal hair, glowing left eye.
Sephiroth's Head: White hair, slitted pupils.
Jenova's Body: small right wing, large left wing.
Genesis' Body: Large left wing.
Sephiroth's Body: Smaller right wing.
Now, this gets especially interesting when one of the Genesis Copies absorbs Zack's S-Cells on the Highway.
The copy undergoes a incredibly intense transformation that mutates him into a state that's unlike the previous experiments, but still contains features of Jenova-like lifeform:
• Lifestream, dark (possibly tainted) lifestream, and orange bubbles spawn from the host. (The orange may be similiar to the
red lifestream currents that burst from Sephiroth at the end of FFVII).
• The reaction contains itself within the host.
• The reaction releases explosively, pouring out.
• The host grows three spider-like arms on either side, and mandibles. All unnatural limbs are now orange, blue, and grey - the colors of Jenova's natural state.
• The host also gains two wing-like structures ending in hands, and a dorsal wing, and feather-like scales are present on the host's entire visible body.
That being stated, the fact that Genesis has G-Cells, and unlike Kadaj/Yazoo/Loz, they're not S-Cells, I don't think that they'd have a similiar effect in re-creating Sephiroth, because they seem to react incredibly differently. In fact, I think that Genesis may actually be the key to the puzzle of the Planet ridding itself of Jenova
IF he can successfully absorb S cells without them completely overtaking his biology, or driving him mad, like it seems to do with the G Eliminator. This may be a result of the fact that the Genesis Copy was still suffering from the effects of degredation.
Unlike anything else so far, Genesis is successfully saved directly by the Planet itself, and seems to represent the ONLY time that the Planet has ever successfully dealt with the adverse effects of Jenova cells in a Gaia cell. When the Planet was attempting to purge the effects of Jenova and the tainted Lifestream in AC, it created Geostigma, by overcompensating for the effects, and was eventually only cured by Aerith. It's likely that it managed to stop Genesis' degredation in what seems to be the same way. That may be a difference between S and G Cells.
With Genesis as the only remaining individual with G Cells, this could mean that Genesis is capable of absorbing this tainted/alien material now, and have the planet successfully combat the negative reactions from the Jenova cells. While the S Cells would likely cause him to undergo a rather drastic transformation, it's likely that the Planet would still be able to combat it within his body. If this is the case, the Planet could use Genesis as a WEAPON and have him absorb all of the remaining Jenova biomatter, and tained lifestream, the Planet may be able to purge the 2000 year old infection completely - though it may result in his death (a poetic enough hero's demise would suit Genesis though).
The main thing that I don't have any ideas about, is what he takes Weiss with him for (a being infused with pure lifestream), unless he's using him (or his biology) to assist in staving off the negative effects of absorbing all the tainted/alien material.
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