How to let users only rename the name, but not the number?

I want to grant the CAD users the right to rename the name of their EPMDocs and WTParts, even when they are released. The number and CADname must not be changable.

I haven't got this working with ootb acl. One solution would be to have a small jsp or seperate action, which let you just rename the name. But how can i run a certain task/method like the renaming under a diffrent user account (e.g. orgadmin)?

...
EPMDocumentMasterIdentity masterIdentity = (EPMDocumentMasterIdentity)master.getIdentificationObject();
masterIdentity.setName(newName);
IdentityHelper.service.changeIdentity((Identified) master, masterIdentity); //have to be executed with user orgadmin
...

Any other solutions are also welcome.