Careful the steps you take from those kinds of thoughts, here. Lemmy is best when it is unified. A split down the middle, even worse, three ways could have drastic consequences for the sort of community, or even segmented communities that Lemmy could become if it schisms.
Lemmy could be a center-left haven for rational thought, or in three years it could be an extremely leftist community fighting an extremely right-wing community fighting a group that wants nothing to do with either, all cut off from eachother with non-political subs and the overall community suffering as a result.
This could all be done with Jerboa with zero input from the admins of individual instances.
Jerboa could send an "application" from each user that registers to the server it chose based on load and location, then inform the user once their account is approved and log them in, them of course getting an email from the instance letting them know where their profile resides.