I enjoyed the thread, but I have a few problems with it.
1) The tree turns its victims into White Zetsu only after draining them of all their Chakra. It is still too early to say what will happen to Orochimaru since we are sure of what his Body change jutsu actually does.
2) The Cursed Mark doesnt let Orochimaru control people, or else the entire Part 1 of the Manga would have been redundant. At the most all it does for him is allow him to transfer his consciousness to said person as in summon/reverse summon. But not much else in regards to mind control.
3) Your making a leap between, White Zetsu can communicate to each other through root systems and can use a technique similar to Kisame's subteranean voyage all the way to White Zetsu can tap into and control the power of the God Tree. These are the same Zetsu that revert back to being Tree's after being attacked by Naruto, these flimsy body is what is suppose to house the power of the Juubi AND everyone in the world.
To me it seems like your on the right track but got over eager and veered off. If we merely look back at what we have seem Orochimaru do with the cursed mark before we know that he can use it to reverse summon/summon himself. We know this because Sasuke reverse summoned him from Itachi's Genjutsu world. I think Orochimaru is going to use that same trick to try and escape from this Genjutsu, since it has already been established as being a viable method.
The seal placed on Kabuto was just a standard Cursed Mark Seal, but we know from experience that Cursed Mark seals can be conditional upon something happening. What if this was a self activating seal? Or what if the condition was SZ moving, since he currently cant move. For instance, SZ said he couldnt move, perhaps Orochimaru was suppressing his movements through the seal, so that when he entired the genjutsu he would lose the ability to restrain SZ, SZ would then be free to move thus activating the reverse summon and freeing Orochimaru from the Genjutsu.
While it is true that Orochimaru seeks after ultimate power he has shown in the past not to be blinded by this ambition of his. I dont think he will do anything bold like attacking Kaguya, he even stated that after being summoned he didnt have the strenght to defeat Sasuke, so I dont think that he is going to have a dog in this fight.