The major issue with upgrading and migration to Cloud is backward compatibility. This process is like an evolution where an entire species will be extinct unless you evolved. Take OTM upgrade as an example, the nonsensical troublemaker Glog XML is forever not backward compatibility. This creates a ripple effect to legacy systems who have to conform to this change. While we are lamenting this issue, what should be done?

Where to Change?
When the product do not support backward compatibility, this raise the issue on where you are willing to invest on change. Usually, there are two areas of change that could be done. The standard approach is to make the change on your end to conform to the upgraded Glog. What happens when the change impact is huge and take a long time? The other approach is to seek the vendor help to raising a product change request to support the backward compatibility?
Transitional Application
You will be in a deadlock when both approaches have difficulty to meet the required change. Thankfully for Cloud, you can now easily create transitional application to connect and translates the changes for backward compatibility. This is a common interim solution to maintain the change impact to minimum. The transitional application will be transition in nature and allows migration or upgrade activities to proceed. It also helps you to conduct full change to the new Glog at a later stage.
In the bid to upgrade for cloud, many applications are not backward compatibility to older versions. This creates a dilemma on where to manage the change. You may want to consider building transitional application minimise the change impact of backward compatibility like OTM Glog.