Probably won't work. Right now a waiting period doesn't make sense for people who already own firearms. Purpose of the 14 day waiting period is to do background checks, supposedly prevent suicides and immediate crimes, and discourage people from buying firearms.
CA already ruled that waiting periods on people who already owned firearms was unconstitutional. So their is a legal precedent already (they can do a background check but the permit must be released as soon as its completed, which is no more then 3 days)
Logically speaking you are right. Although, the rap back system would only check for criminal issues right? If mental health issues are not checked then they wouldn't even consider it.
Im still not sure on the legality of Hawaii's medical background checks, The law says you are required to sign a medical release, it says nothing about what other information you must provide (such as doctors information) You are not required under the law to get a medical clearance, HPD is allowed to check your status as per your signature,
I believe forcing you to get a medical clearance (if your health provider decline to answer their questions, you do not have a doctor, or as the case with kaiser they dont provide clearance but instead provide your medical information) would be unconstitutional. They can only deny your permit based on confirmation of a medical reason not on lack of confirmation that you dont have one.
That being said i believe the case would still be the same as the background check, Once i have 1 gun having more dont make me any more dangerous, Do the check, let me have my gun and get back to me latter if their is a problem.