Yeah but possibly a little bit difficult to code with TMLs restrictions (they aren't many, but they still exist).I wouldn't say it is. Though, there may be mini dungeons in the mod after release. Who can say? Be nice to have more mini dungeons.
Though, a Crimson/Corruption-themed mini dungeon would be cool. Spawn in after some boss perhaps? You could go through them and a new boss (Corrupted/Crimson) would be waiting at the end. That'd be cool. @Bullseye55