Relic Castle

Hey, so I’m adding different color variants of each Pokémon to my game, and most of them are simply going to be randomly mixed together within their indigenous routes and such. But some of them - only a handful - have a different type as well (like Alolan forms) and will need to appear in a separate location, i.e. forms 0-3 of Litwick appearing on most routes specified in the pbs, while form 4 will strictly appear in map 28, 29, etc. Or having Alolan Rattata appear in place of its regular form on the same map when it’s night-time. I’ve done a lot of googling and played with the script (which I’m still not an expert at) a fair amount, but am beginning to wonder if this function is beyond the game’s capabilities. Or am I missing something? Any help would be very much appreciated.

Edit: I do hope this question is in the right place. Apologies if it isn’t and please let me know.