Concerning PBKFD2, 2048 iterations was designed to slow up brute-force attack. But 15years after this design, 2048 iterations is quite weak. Do you think we should make more iterations ?
Rather than enable more iterations, we might as well as creating new BIP as successor of BIP 39. There are few improvement that could be added such as,
1. Versioning system
2. More iteration during converting mnemonic to seed if passphrase isn't empty.