The luau idea for the tapus sounds like it would make a good repeatable scene after you've caught them, but I'll have the tracking/breeding/capturing scenes be solo like normal.
Sol/Lun are considered "Restricted Legendary Pokemon" on Serebii, those are the ones that I'm making mandatory like Mewtwo, Lugia, etc
Necrozma is also in this group s will also be a mandatory catch
The Ultra Beasts have their own section, which is why they're getting side-scened, the same goes for Paradoxes
This page here is what I'm using to categorize the Legends
https://www.serebii.net/pokemon/specialpokemon.shtml