Great article! I’d like to add a few practical points to reinforce the design and type safety around heterogeneous assets in Sui Move:

✅ Since dynamic_field::add<K, V>() requires the store ability, assets like soulbound tokens (which only have key) can’t be stored directly. Instead, store only their ID and listing metadata, which do have store.

✅ Best approach: separate collections based on ability constraints:

• VecMap<ID, ListingWithAsset> → for key + store assets (e.g., transferable NFTs)
• VecMap<ID, ListingMetadata> → for key-only assets (e.g., soulbound tokens)

✅ Add a runtime asset_type: String tag to metadata. This enables you to identify and safely handle asset logic (e.g., transfers, display) even after type erasure.

✅ Phantom types are excellent for compile-time type tagging and preventing developer misuse (like accidental transfers of non-transferable tokens).

This modular structure is scalable, avoids Move ability violations, and allows for flexible marketplace design without sacrificing safety. Great work on explaining it so thoroughly!