I've been thinking about doing something similar, but on a much smaller scale.

For the swap, you should be able to use the taint method so that the BTCs and BTUs get to their proper destinations:

• Before the fork, you each depsit 60k coins into a multisig address, for a total of 120k
• After the fork happens, the escrow address will contain 120k BTC and 120k BTU
• You obtain a properly split (non-replayable) BTC UTXO on the Core chain, and Roger obtains a properly split BTU UTXO on the BU chain
• You send your BTC UTXO to the escrow address, and Roger does the same with his BTU UTXO (let's say they're 1 BTC/BTU each)
• The escrow address now contains 120,001 BTC and 120,001 BTU
• Create a multisig transaction that will send the original 120k BTC plus the 1 BTC TXO to an address you control, get it signed, and broadcast it to the Core network. This transaction will be unspendable on the BU chain, due to the 1 BTC TXO.
• Create another multisig transaction that will send the original 120k BTU plus the 1 BTU TXO to an address Roger controls, get it signed, and broadcast it to the BU network.  This transaction will be unspendable on the Core chain, due to the 1 BTU TXO.