I have customers who have upgraded 2008r2 -> 2012r2 -> 2016 without any real issue. You should probably stop & disable BESClient and BESRelay until finished, so the client doesn’t reset if the OS upgrade encounters an issue and rolls-back.
Note for Upgrades you won’t be able to use a captured image, you need original 2012r2 and 2016 media.
In most cases I advocate for wipe-and-reload, but for the most part upgrades seem to work ok.