I was actually thinking a return address would be a good use for the arbitrary-message-to-receiver OP_DROP transaction type.
Maybe make a convention that bytes be a JSON dictionary, so it could be:
{'return_address':'n2cGZYsiii1uAiDPM6ipPBqqXa4Z9bXh2t'} OP_DROP ...etc...
... which would be inefficient (58 bytes to encode the 20-byte return address) but wonderfully extensible.
And again: I'd like to see experimentation on testnet.