An insightful proposition. Cross-chain NFT metadata management remains a technically demanding challenge, particularly when ensuring data integrity, provenance, and verifiability across heterogeneous chains. Smart contracts would require reliable oracle networks or decentralized storage solutions like IPFS or Arweave to maintain consistent metadata references. Gas fees on high-demand chains like Ethereum pose a scalability barrier, potentially limiting frequent index rebalancing or metadata updates. Additionally, the NFT market is already approaching saturation, with declining engagement metrics across several ecosystems. Integrating NFTs into an index model must carefully assess liquidity depth, valuation standards, and the risk of over-indexing volatile, thinly traded assets. A prototype addressing these variables would be crucial for credibility and resilience.