I am not sure if it exactly meets what you are looking for and I don’t know if it will do much for a neuron that has already been given to the NNS, but ICRC-75 was designed to specifically give SNSs the ability to exactly this.
An SNS can deploy an ICRC-75 canister and add the Generic Functions for Managing lists of accounts, principals, and/or values. So an SNS could easily vote to add and remove members to a list and then the members of this list can ‘do things’. For example, a canister can be set up that looks at the list and only lets people on that list execute certain functions. Or it can effect a multisig where X number of people from the list have to approve of the calling of another function.
Please see more on this thread: ICDevs. DAOs Project Final Grant Post