Bigshot does allow for head/tail, and it works pretty well. If you don't want to go the automated script route, it's really all about macros and having 2 monitors or splitting the screen so you can see both at the same time.

With good macros, it's not hard to flip between 2 characters dealing with situations at a click of a button and a quick keyboard combo. You have one for casting each of your spells, that will stance as needed for the spell. Remember you can string together more than one command line in a macro. This is the only way to really be the one in control as opposed to a script.