Agreed.  I just want the thing to remember to be easy to remember, and also safe to record openly if necessary.

I'm not in agreement with this assessment.  (But you've got me thinking!)

First, a minor part of the disagreement is that if I were to use the chess approach, I would select a much, much more obscure game to use for the passphrase data.  With easily up to a million recorded games, that adds another 20 bits of entropy to my BrainSeed.  And I think there is more obfuscation possible.  But let's say that the BrainSeed has 75 bits of entropy.  In normal BrainWallet cracking efforts, the target is to try derived addresses and check if there is BTC there.  However, here the target is to find a passphrase that has to be used in conjunction with another passphrase.  So really there is another 75 bits of entropy to deal with.  And then the iterative process adds a lot of time delay between each cycle.

Second, my real desire here is to create a Brainwallet passphrase with high enough entropy that the standard cracking efforts won't uncover.  And with BIP38, they would have to crack another high entropy passphrase to get at the encrypted private key.

You've got me thinking hard about how realistic it is to figure out the obscurity of the overall approach.  I guess the real lesson is to make the underlying structure highly obscure.  (I'm quite confident that my own underlying structure is highly obscure.)