Here's an appropriate theme for the unlocking of the GS Ball: https://www.youtube.com/watch?v=FeM9GjwPXOk&index=24&list=PLj-ru-1cx_tlMEbtwQ1V4-ATAkfXNHoyD
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
>Though I do see the catch of it being based on a limited, Japan-only distribution from 20 years ago. But I guess that's more in Easter egg territory - the plot can be explained and can make sense without having seen that event, but seeing it does add to the impact for anybody who has enough interest/awareness of the series's history.
Don't forget that it would be easy enough to include the GS Ball event in the localized Crystal re-release. The event itself was translated, except for the News Machine interaction with Chieko, which was DLC to begin with. So yes, we could see the event for ourselves.
Either way, Chieko's flashback would explain it sufficiently.
>- Why did Neo Celebi ask to be sent to that time period? Was it aware of the war/fire beforehand and specifically wanted to exploit it?
Celebi should definitely be aware of what happened in that period, and Neo Celebi obviously has its memories. As for what exactly happened... The GS Ball may have been the reason for the war. What if two regions fought over who gets to unlock the GS Ball? I'll need to think about this some more.
As for your points about the timelines... I should be clear about this: There aren't any major deviations between the timelines as far as Kanto and Johto are concerned. The Mega Evolution shtick only affected Kalos and Hoenn to any noticeable degree. So Neo Celebi doesn't actually discern between the GBA/DS and 3DS worlds... It ends up in both, pretty much like how most events happen the same way in paired versions. The actual deviation will be a result of the humans' roles.
Put another way, to Neo Celebi there is no difference between those two timelines (it can only detect changes in the period it is in), but to Silktree there very much is because he is actively trying to undo what happened in the bad one.
> How does Neo Celebi change the plague to wipe out humans in the GBA/DS world?
It will pretty much braindwash all the wild Pokemon in Kanto and Johto to do its bidding, which means wiping out humans. With them out of the picture, the disease can't spread to Pokemon.
>That could be a really cool way of giving Ecruteak a Mauville-esque upgrade. Showing both towers surviving to the modern day in all their splendor.
HGSS foreshadowed the Brass Tower being rebuilt, anyway.