In SCCM 2007 I could apply client patches during the config manager client install task of an OSD like thus: PATCH="%_SMSTSMDataPath%\OSD\AH2000A6\hotfix\KB2994331\Client\x64\Configmgr2012ac-r2-kb2994331-x64.msp"
Can it be done the same way in 2012? the hotfixes no longer reside in the client install folder, so the .msp's would have to be copied there manually and the client package updated. I've found at least one post where this was being done, but I cannot find any official MS KB saying this is supported or not: http://www.deploymentresearch.com/Research/tabid/62/EntryId/189/Installing-CU3-for-ConfigMgr-2012-R2.aspx