Obviously any change in the database used for wallet.dats will be rejected since it will break compatibility with all tools that depend on the structure.
The only thing that users need is the "xprv" value if it is HD wallet or all WIF-encoded private keys if it is not. By having private keys it is possible to recover everything else. Am I missing something? Both things can be easily written on a piece of paper and expressed in text as needed, so they are as "standard" as they could be.