Let's see:
- Hide & disengage be changed to be actions (as per 5e rules)
- Cunning Action (level 2 rogue feature) to be reworked to include hide & disengage (as per 5e rules)
- Cantrips no longer causing surface effects in addition to causing damage and having their 5e damage values restored
- Monster HP and AC values closer to their actual MM stats
That's it for me basically.
Yes. Close that can of worms before the ripple effects spread all over the place.