No issues there. He won't be able to upgrade 2/3 of them. Lots of time saved! 😂
Seriously, I have several apps and plugins extending classes in the /system folder. That means they're all dead for v5. So far, I don't like the direction v5 is taking at all. No matter what awesome tools you may have in place, being unable to overload (almost) all classes like before is a huge issue.
Well, that's it for me for now. I won't say anything further until there is more info about those "awesome tools" you mentioned. But I don't have much hope for them.