If a lawyer violates the code of ethics, he is to be the first one can access your Million BTC for himself. you must be thinking to do not just giving up the seed to the lawyer. He is a human who has a mind and feels if gets stuck needs the money asap and doesn't know how to get it, your seed is very easy to access and immensely helps him.
I think the seed needs to be split to the lawyer and the people you are going to give the funds in case of drying , with this I'm sure there is no one that can take the funds unless they will agreed to each others claim.
That good idea, but the lawyer needs to learn more about the split and how it works, because in some cases many people don't know how to recover (as i know split seed is still new), so when the heir dies, some lost shares and part of seeds, that make lost bitcoin forever. Or maybe better to use multisignature than Split?