Customizations for 12.2 that do NOT require online patching

Has anybody in the community been through a 12.2 upgrade project where they had to make their customization's or 3rd party software compliant with 12.2 that is willing to share their experience?

As you will likely already know, 12.2 now dictates that software integrated with EBS is done quite differently to how it was done previously; the vast majority of the Oracle documentation is all about how to make your software 12.2 compliant whilst ensuring it can be patched online; however, the documentation does clearly suggest that customizations "can" be added to 12.2 that do not need to be patched online and so I'm looking for information on how best to do this.