Anything that happens outside of the normal detailing process (i.e you're coming up for orders) the command will need to be involved in some form or fashion since it affects their manpower. For the RAD, the CO will have to endorse the request before it is sent off to PERS. If this request is being submitted significantly before MSR, said individual better have some very good reasoning (and/or personal issues). BTW, some personal issues can be dealt with differently, which is why it may be a good idea to talk to the COC. If we're only talking a year or less from MSR, said individual still needs a valid reason, but it doesn't raise the red flad quite as high as the other (i.e. longer than a year out).
Since the RAD request would be before MSR is complete, the CO will have to state in the endorsement that said person's billet may be gapped...basically saying that a relief is not required prior to executing the separation orders. A RAD request is NOT a special request of sorts. It's something we all (officers) have to do when and if we want to leave the navy before retirement, unless you are submitting a resignation which is something altogether different and has different requirements.