there are a couple of hacks that i've used to deal with "unusual "actions".
to add an action that does edit differently from the declarations you have in the CRUD, the new action would route to a URL that is the same as the edit url except that you have include a segment that the CRUD checks to determine the alternate edit field list. then use the trick elsewhere on this forum to clean up the URL. alternatively the action URL could go to a small function that sets a flag in sessions then redirects back to the edit URL and just have the CRUD look for that session flag to determine the field list.
i've had to do this sort of thing and a complex user registration process because, for example, you don't know the id of an added record at the time the success message is set so you can't use the message to jump yourself to the next step so instead i go to a redirector, and by then the id is knowable. ok i digress but you get the general idea.