Reference: Regulation (EU) No 965/2012 on Air Operations, Annex II (Part ARO, ARO.GEN.310, ARO.GEN.330), Annex III (Part ORO, ORO.GEN.130)
Part ORO does not mention anymore the notion of acceptance/acceptability of nominated persons. This is now replaced by the notion of changes requiring prior approval or changes not requiring prior approval.
During the initial certification process, nominations of personnel in general are considered to be part of the verification of compliance performed by the competent authority and therefore covered by the issuance of the AOC.
Regarding changes to certified organisation, the notion of changes requiring prior approval/changes not requiring prior approval applies and therefore, a formal approval of certain change is required. Guidance is provided through GM1 ORO.GEN.130(a) and GM3 ORO.GEN.130(c). Likewise, upon initial certification, the competent authority may agree with the organisation on a more specific scope of changes that do not require prior approval, on the basis of ARO.GEN.310(c), and within the limits of the applicable requirements. Items not required to get a prior approval are managed by the organisation based on a procedure approved by the competent authority for the management of such changes. In any case, these changes have to be notified to the competent authority which will verify compliance with the applicable requirements (cf. ORO.GEN.130(c) and ARO.GEN.330(c)).
Regarding the specific case of the safety manager, it should be noted that there is no requirement for a safety manager at an implementing rule level. The nomination of a safety manager is one means to comply with the IR objective. Therefore, a change in safety manager is not listed in the GMs to ORO.GEN.130: A change in safety manager is not considered a change requiring a prior approval from the competent authority, unless, the accountable manager fulfils the role of safety manager, in which case a change would obviously require prior approval.
The above references are those to Regulation (EU) No 965/2012; the same provisions are included in Regulation (EU) No 290/2012 (ARA/ORA).