But in that case why you would need to use GrapheneOS at all? Without security you cant have privacy and OS with security as priority cant just add hole in the system because it would allow to bypass all security features added on top of AOSP and AOSP features too. Most features people use root for can be achieved without root by modifying Android Framework itself with SystemUI/Settings app

If you wish so you can gain root privileges on your own in your own build or with modifying GrapheneOS existing builds. It wont be compatible with GrapheneOS provided updates because of signature mismatch