This is a DoDMERB question, so it would be better to ask it over there in case any poster has experience. For example. KP2001 is a flight surgeon, but rarelyy if ever posts on the ROTC forums.
As far as the waiver process goes it is a case by case and the source whatever ROTC program going he is going through...i.e AROTC, AFROTC or NROTC. One branch may waive while another may not, it happens all the time that the AF could say yes, but Army and Navy say no. Additionally, the source must request the waiver, he cannot, so you will have to wait to see if he gets DQ'd and than to see if they will request a waiver.
You just have to get his medical paperwork in order and expect to go through the process.