On Fri, Feb 12, 2016 at 5:02 AM, <jl2012@xbt.hk> wrote:

> Seems it could be done without any new opcode:
>

The assumption was that the altcoin would only accept standard output
scripts.  Alice's payment in step 2 pays to a non-standard script.

This is an improvement over the cut and choose, but it will only work for
coins which allow non-standard scripts (type 2 in the BIP).

I guess I was to focused on maintaining standard scripts on the altcoin.