Considering the high amount, and the long duration of the escrow, you may want to consider a 2-out-of-3 multisig: OP holds 1 key, and 2 escrows each hold one too. That way, 2 out of 3 parties can always make a transaction.
This. There's very few people here who should be trusted to hold onto such an amount and these kind of figures can make even good men turn bad. Maybe contact theymos and see if he would be interested in being one of the people.
I agree with that you said Theymos should be among the escrow cause he is one of the respected person on this forum and it only trusted legendary member can hold such amount. However, it will also be better if the btc is split as LoyceV said.