I really want a game that is transparent about how things are built. Both the mathy bits and the ribbon bits. And then clear procedures for the GM or player to build their own.
I'd like a disclaimer that if someone uses the above desired-by-me rules to build something, balance is as good as what the players and GM bring to it - in other words if someone creates their owlbear (mountain heritage) monk hexblade, it may have slightly less or more DPR than the other player's gnome (air elemental heritage) druid school of divination. And if that DPR disparity exists - well
caveat emptor.
In terms of "under the hood", here's what I'd like revealed
- Class
- Race (changing the name of that to heritage or folk would be good)
- Spells
- Magic Items
- Artifacts
- Equipment
- Backgrounds
Also, epic levels (up to 30+).
More robust uses for Inspiration, especially ways to engage with Ideals, Flaws, and Bonds.
End of Session procedures.
Random Dungeon and Terrain generation tables.
Robust PVP rules.
Instead of ASIs, increasing ability scores would be through failing at a skill check with those scores - basically a parallel advancement track for each ability.
If I was to get really crazy, I'd love to see an optional "fail forward" or "succeed with cost" mechanism provided.
If I was to get super duper crazy, I'd love to have robust rules for social encounters (Burning Wheel's Battle of Wits? 4e's Skill Challenges? Other?) that could parallel physical combat encounters, but lean on WIS, INT, CHA.
Will there be an A5E MM? (A5E Manual of Monstrosities?)