EIP3386 proposes to create an interface to the exchange between NFTs and their derivative ERC20 tokens. This involves the transfer of NFTs into the pool in exchange for minted ERC20s, and the burning of ERC20s in exchange for NFTs from the pool.
The issue: https://github.com/ethereum/EIPs/issues/3384
The pull request: https://github.com/ethereum/EIPs/pull/3386
Existing examples of this concept include NFTX, NFT20, WrappedKitties.