Invoice Module: Fill Invoice address from related contact or account

How hard is it to make the same JS action fire when entering a contact as does when entering an account in the invoices module?
We have many invoices that are sent to private persons (but mainly we do have companies as customers). It would be wonderful not to have to type in the contact details by hand when no account is present! (and it would be nice not to have to create lots of dummy-accounts just to make this work).

any ideas or experiences?

Same problem here.
Any solutions yet?