Hi Graham,
It can be done, but it just depends on what you want to get out of the form: graphics / dynamics / data???
We use Id/Ps mainly for background graphics and buttons to use in LC. Our current approach is to generate a frame or masthead in "51,51,51" v9 or "103,103,103" v8 and below: to generate a frame or header to CLAIM the Adobe space. This brings the form into the Adobe window instead of just an A4 page plonked into the standard Adobe look and feel.
Yes, it is possible to import; yes you will (probably) have to adapt the javascript, but why bother. Use the Illustrator for backgrounds / graphics only and import as a JPEG / PNG. That way you can deal with the form development / scripting in one environment - LC Designer....
... imho....
Going back to the question, if you want a dynamic form, comp it in LC - that way people won't be disappointed with the final result!! If you get people pumped up with Illustrator and can't deliver in LC, then there may be a lot of faces around the table... again imho...
What does the user want???
What does the manager want???
What data do you want???
If the form is for paper only, then IL is fine, but for electronic IL takes a back seat...
N.