The other thing that could be a sell is retention. Retaining new grads beyond a year or two is notoriously difficult. If you’d have data or proof that this approach significantly increases retention and its because of the group setting, that could make the premium laid worthwhile.
You still need to convince companies to trust your assessment method: not a problem while you only have new grads from the very top schools, but would be a problem if you open up to all colleges.