My contribution would be from various games in the OSR space:
I want to get rid of skills.
In 2000, skills were hot stuff, but "roll a d20 to succeed at this narrow application of an ability score" is a snoozer. We also wind up with certain ultra-significant skills (PERCEPTION) and some fairly worthless skills that relies on a DM to make them useful (like most INT skills).
I'd rather replace them with traits that just....give you benefits. Rather than a Religion skill, your character is "Religious" and they can invoke it just to know things about religion instead of having to roll. Rather than a Perception skill, your character is "Perceptive" and immune to Surprise or something. Now, I don't need to pump my Dex just to have a good stealth roll; I can just be "Stealthy."
Correct. The Escalation Die exists as an elegant solution to the dominance of the "alpha strike."
I'm fond of escalation mechanics, and I don't like how an alpha strike can just ruin what could be a fun encounter, but fights in D&D are typically
three rounds, and I like it that way. I want my fights to be quick and uncomplicated, to get out of the way fast so I can get back to the storytelling. Could be something to bring in for Legendary monsters or something, though, where a longer fight might be nice...but long fights take up a lot of table time, too.
The At-Wills in 4E were generally more interesting than the At-Wills in 5E.
One relatively easy thing that could be added to 5e today is 4e-style at-wills
based on your weapon.
The idea is that cantrips and martial weapons are largely mechanically equal and similar in design space. Cantrips just tend to have more interesting wrinkles than weapons. So give martial weapons some neat sauce. Bows can ignore cover. Greatswords can do a green flame blade style "cleave" effect. The "light" property is already kind of this (because it enables two weapon fighting).
While not a "bell curve", it is centralized more around the mean, making the typical result more common and the extremes less likely.
I think changing D&D to make the typical result more common just
destroys the heroic appeal of the d20 mechanic. The d20's swinginess is good, actually, and I will die on that hill, hahaha.