I've been play testing the UA rules for a year. It's pretty seamless. There are some new systems that get added on (e.g. weapon masteries) but nothing like what you suggested for paladins, which is an entire rebuild of how the class works and would be incompatible with the current rules. Even nu monk, which got the heftiest changes, still uses the same chassis.
The 2024 rules easily handle 2014 characters and adventures. Which was always the point.
I'm not criticizing your suggestion - they are interesting ideas. But the claim that an engine rebuild was the point of 2024 is dead wrong. They made all the changes very much within the existing engine. Which is why your interesting ideas were never going to happen in the updated rules, though they'd probably be pretty cool as house rules.