Sorry to sound daft, but how would doing this be any different than using a "optional phrase". I still have the limitations on the number of characters able to be utilised.
Yes, the limit is imposed by the windows "tree view" control at 260 characters, and it is not something I intend to change because I would basically need to use something other than a treeview and I don't think it is a real problem for most users. As you say, you can get around it by editing the xml directly.
I was suggesting that you use a payload-list so that you would have a payload {1} that you could use in your command logic. It is not as powerful as using a phrase/value payloadXML but you could still do some interesting things with it.