Nothing ever killed my buzz more than scoring a critical and then not conffirming it.These and only these. I'm pro-"players roll all the dice," however, so spell attacks in 6 (though not reducing the number of saves) are good with me.
I'm down with reviving confirmation rolls for critical hits, which was in 3e. Without them, the game is too swingy towards the monsters.
Unlike most of the options people want, these actually have a chance. Since 1D&D is backwards compatible, a ton of things simply cannot change. These are add-ons, rather than core changes, so they can more easily be incorporated.1) Monsters with more varied abilities;
2) Bloodied Condition;
3) Skill Challenges.
1+2 are a big nope from me, for reasons that other folks have already spelled out. Healing surges were an attempt to incorporate video game mechanics. Never a fan.Now, 4E is not my favorite edition of D&D, but there are some good things that I like in that edition:
1. Healing surges; HD healing in 5E is just clumsy and worse version of healing surges, and I believe it was change for changes sake as not to remind people of 4E.
But why? It was great. It was reliable, while HDs are RNG cluster #$%!.
25% of you max HP is a good amount.
You can have a number of healing surges equal to double your proficiency bonus plus your Con modifier per long rest.
Some 8sub)classes might get a bonus healing surge or two, or more on later levels.
2. Second wind; closely connected to no.1 here is Second wind. Remove it from fighter and give it global usage as a Action. Heal yourself for 25% of max HP, number of times per long rest equal to your prof bonus.
3. Short rest is 5 min. This is self explanatory. 1Hr is NOT a short rest.
4. Attacks opportunity do not spend your "reaction slot", but are on separate once per turn(any players turn) counter.
This would help melee characters keep enemies in melee range or suffer AoO more easily.
5. More things provoke AoO: casting spells that are not melee touch or close blast/cone(without Spell sniper feat), ranged attacks(without Sharpshooter feat), moving more than 10ft within melee range,
6. return to 3 saves or defenses, I'm good with what ever. But it's more fun as a PC to roll all "attacks", so from player perspective all spells could be spell attacks, vs one of 4 defense.
Have Fort save/defense be str+con mod
Reflex save/defense be dex+int mod, and
Will save/defense be wis+cha mod,
Jeez, how could I forget?? THE WARLORD.I'm not down with any of the changes mentioned in the OP. Most of what I want from 4e is monster design, epic destinies (and possibly paragon paths), the bloodied condition, the forced movement rules, and curses and diseases on a track. Oh, and skill challenges.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.