There is a similar conversation on the Facebook group from last week.
Opting out doesn't affect your ability to order things at the hospital but expect no one at the hospital to have a clue about what opted out docs can and cannot do.
Since the hospital is a big potential source of problems that could affect my practice, I will keep outpatient credentials for now, if only to know better what they're up to over there. It also gives their docs more opportunities to talk with me about what I'm doing. You'd be surprised at the misunderstandings with your fellow docs. Several thought I was sitting around counting my money at an MDVIP type concierge practice long after I'd been marketing and talking about this around town.
Don't bother with the credential manager. I'd start with the CMO or VPMA at the very least. You don't need to tell them or advertise that you'll be helping patients find less expensive lab and imaging options but you can find common ground with them on some issues.