I've had the same thought. Wish wallets would let you choose 12 or 24. I'd prefer 12 and a good passphrase. I don't need as much entropy as atoms in the universe
Discussion
#[4] let you choose
Most wallets do let you choose if you generate the key outside of the wallet with your own entropy.
Within the wallet you would be selecting restore
existing, rather than create new.
Every bitcoin wallet that will ever be used already exists, it just needs to be discovered.