Yep, just as I suspected my request to add a remove properties api was rejected (as a duplicate to a non api variaty of the request). No schocker really.
But I do have a better idea how I can better handle this without resorting to evil (but really useful) hacks. First the wizard task will keep it's own set of properties outside of the ant Project, reflecting non-user properties as pre-existing defaults. The Do and Undo elements will behave more like antcall, they will have a target attribute that an instance of the project will be created with the properties from the wizard task, like antcall. Body tasks will still be supported in lieu of the targ attribute (if the code isn't to henious), but a synthetic target will be created in the project containing all of those tasks.