Don't the Ivies provide something like this already -- a likelihood of admittance letter for student athletes. They don't give athletic scholarship, as I understand it. But I know kids who sign this letter on signing days at school signing ceremonies. I think this is a completely non-binding thing.
SD,
Not exactly. Likely Letters come from Admission to inform a recruit they are extremely likely to be admitted (after the recruit has verbally committed to the Coach) if the recruit keeps their grades up, doesn't commit a serious crime, and provides an Early Decision application. There is nothing to sign officially other than your ED application (which is binding) and application $ check. Likley Letters are intended to compete with NLIs for athletes that Ivys want. Ivy recruits can sign a blank piece of paper at signing cereomonies (as my oldest son did) at his high school.
Some of the more savvy Ivy recruits will verbally commit, apply RD then change their online application to ED (binding) once the Likely Letter is received by the Ivy athlete from Admissions. I would only consider this if the recruit has other options and a good amount of leverage.
Let me know if you have questions or if that didn't clarify.