This rearranger does also swap tileset data such as passages and terrain tags. However, if you save in RMXP after making the changes via this plugin, those data changes will be undone. This plugin tells you this, and tells you to close RMXP without saving to ensure the changes remain changed.
I've always considered legendary Pokémon to simply be very rare and unusually powerful. They're not unique (except maybe for the artificially created Mewtwo and Genesect; Mewtwo's clone origin lore is too ingrained in me to ignore, and while I don't care about Genesect, it has its Drive thing...
I'm curious how many people have considered making changes to the existing Pokémon evolutionary families. I'm not talking about just changing evolution methods or adding a new evolution/prevolution. I'm talking about things like removing a species altogether (while keeping the ones that used to...