The choice of a side could start in the archives.

[Waitdire]

In order not to simplify the early game due to some "strong" abilities from the shadow or moon side, the choice of worldview could begin after we bring the latest Iridescent Gem to the archive. This event literally includes a brawl between gestalts and shadows in Lunar Grotto, and this is a good moment to choose which side you are on, and it will also make lunar/shadow privileges more daring, because getting the third Iridescent Gem can take from 11 (if very lucky) to 31, to 51 days under normal conditions. Wilson may be an exception, but this will essentially give him a new role in the game that no one else can do except him. Maybe yet Wickerbottom, but it's harder to do it for her.