It looks like not being possible easily.
schema / srcSchema can't be queried for, so you can't create e.g. a technical workflow for monitoring that.
There is also no published API for doing that via Adobe I/O calls.
One potential way might be to simulate user login to get the access credentials and then try to call the same API call which the UI is doing /rest/head/cusResourceBase/byText?_order=lastModified desc&_lineStart=0&_lineCount=30
Though that won't be easy and the API etc. may change any time as it's normally not supposed to be used for any direct calls.
Also any admin user will have full access to custom resources, there is no way to limit the permissions among the ADMINISTRATION role.