I was thinking about such a module myself lately. Going breifly over your code I have some suggestions, comments:
1. jQuery, isn't good - if a user has javascript disabled then she will see all the fields. Maybe you can make the field's #access = FALSE
2. You might use menu_get_object() and menu_get_item(), it can be more legant then checking arg(0) && arg(1)
3. Passing the step in argument doesn't sound right, it should be some internal variable - how to do it exactly I don't know, as the $form_state['storage'] is being rebuilt every time you re-show the node form.
4. Maybe to make this module more robust, you should make hook_multistep_info(), that one can define which fields should appear on which steps/ conditions.
5. You have some tabs instead of 2 spaces :)
With all that said, have a look in CTOOLS module, I think there is a module there that deals with something similar.
Anyway, thanks for the module.
Comments
Comment #1
vkareh commentedThank you for all your comments! I think these are all great ideas.
I hope this is at least useful as a starting point.
Comment #2
vkareh commentedFixed the jQuery issue. For the others, see responses below: