Your approach would work. Any AE that has the permissions to create a content instance under the container can set configuration data this way. The CONFIG-AE in your example would then need to apply the new configuration accordingly. I am not sure, though, why this AE would be an IPE? With what would it provide interworking functionality?
Nevertheless, you should also have a look at TS-0001, clause 10.2.8 "Device management" and the whole of TS-0022, "Field Device Configuration". Here, oneM2M specifies specific management resources to manage nodes in a oneM2M deployment. This might look like an overkill at first but since the resource types defined there are well aligned with other management technologies this might be worth the efforts.
Depending on your infrastructure you might also want to look at TS-0005 "Management Enablement (OMA)" and TS-0006 "Management Enablement (BBF)" in case you are working with remote management technologies from OMA or BBF.