Nebulous
Legend

This is just for fun. I like 5th edition, but there's still some things I would change.
So let's say in some alternate universe that there WAS an updated 5e.
What would you want to see? For me, for one, I find the layout of the
5th edition book very hard to navigate through. I can't find what I need
quickly except for alphabetical spells. My players all say the same thing,
and they're a clever bunch.
I would like to see unique spell lists for the Illusionist and Necromancer and some other
speciality wizards. Give them at least one spell per level that no other class can
duplicate. Not a class ability but an actual spell.
Ramp up monster toughness and reintroduce the Bloodied condition from 4e.
Clean up the Stealth and Hiding and Perception and Invisibility and get rid of this
ambiguity stuff.
Add some kind of basic IDEA for at least creating/buying/selling low level magic items,
at least consumables up to 3rd level. Or better, just add a whole DMG chapter explaining
how to incorporate it.
I sort of miss Touch AC from 3e, it just makes sense logically.
Redo Inspiration so that it's a fun mechanic. After 2.5 years of playing 5e, we all
consistently forget about it constantly.
I guess what is cool, and has been mentioned in other threads, that these can all
be house ruled in fairly easily. Well, adding new spell and new monster abilities isn't
easy per say, and coming up with a balanced magic item cost system would take some
tinkering.
There's probably more I'd like to see but those sprang to mind.