Auto assign to a membership package with member registration

Hi all,
as I am planning to use a free listing site, I have created a single membership package, free of charge. This will go for almost a year.
Is it possible, during one’s registration to auto-assign to this free membership package, whithout having to choose “Free Membership” button.
Is it possible? (even altering the code a bit)
Thanks

Tip for next version
Maybe a checkbox “default for new members” besides membership packages, would do that and will be usefull to auto assign memberships to new members.