I think reversing transactions is not likely to be acceptable.  You could add an opcode that requires that an output be set to something.

[target script] SPENDTO

This would require that [target script] is the script for the corresponding output.  This is a purely local check. 

For example, if SPENDTO executes as part of the script for input 3, then it checks that output 3 uses the given script as its scriptPubKey.  The value of input 3 and output 3 would have to be the same too.

This allows check sequence verify to be used to lock the spending script for a while.  This doesn't allow reversal, but would give a 24 hour window where the spenders can reverse the transaction.

[IF <1 day> CSV DROP <live public key> CHECKSIG ELSE <offline protected key> CHECKSIG] SPENDTO <live public key2> CHECKSIG

Someone with the live public key can create a transaction that spends the funds to the script in the square brackets.

Once that transaction hits the blockchain, then someone with the <offline protected key> has 24 hours to spend the output before the person with the live keys can send the funds onward.