I watched a Youtube video where a reviewer said it was possible in earlier versions to make pokemon attack the player directly on the overworld map as well (and the player was able to damage pokemon) I would really like to see that as an added option. It would allow for certain custom gameplay scenarios even if the machanic would be broken, to resolve that it is possible to not allow any drops or experience by this kill method.
Aside from that It would be convenient to be able to change a setting that would make the max amount of certain similar pokemon per chunk/biome/tick configurable. So that I would be possible to only see 1 at max of every kind.
For Spawn of Psyduck a more easy method to add missing pokemon to certain biomes would be to just be able to define the "typing" of pokemon you'd see per biome instead of manually adding every single pokemon allowing for a quick manual setup that is future proof until a new version would be released.
Thanks for reading.