In the Fire Emblem community, people have figured out how to import tilesets from one game to the other, and magically their method also ports over all the metadata for the individual tiles, such as what graphics comprise what tile, what avoid/defense increases each tile may offer, the movement costs per tile, what background and palette to use, and other similar data.
But no one understands how this data is being ported over, or how to locate and edit this individual data. I suggest corruption, as most people in the Fire Emblem hacking community aren't familiar with or bothered enough to use an understanding of ASM to figure it out--but no one seemed to understand how helpful, and somewhat easy, corruption is for figuring out data.
If you're really open to the idea, I can link you over to help out some peeps. This would probably be more concentrated efforts than merely corrupting ROMs at-large to figure out where some data may or may not be.