I was simply thinking of the serialize(tx_dict). I was thinking you would right your own (or overwrite) the serialize_script method. I mean there are less than 100 op codes right?
It worked....
Transaction 5e4cf125218fcab2746303485ce3a2a74dc12271f678e851fc95fd97cd0153e4 puts "Hello World" on the blockchain
Transaction 602c4d614351ee615ee1dc280c16a4cf962ccc928a8c3a0dca6f9ccd46104976 spends "Hello World" on the blockchain.
Interestingly... the script debugger says OP_SIGCHECK failed... but it didn't. Also, the funky output script does an interesting job of making the coins quasi-anonomized.