I like the growing list. This brings up the flipside question for me:
What would I change?
1) Flatter math - 5e has shown that the "bounded accuracy" works well to make a single monster stat-block last longer across levels (without having to constantly make "bigger" versions. Now, I wouldn't go anywhere near as far as 5e did, but something like a +1 prof bonus for every three levels? I think it would work.
I'd concur, the ever escalating value was for me too high in 4e. Tighter bounding while still allowing the need for minions et al.
Also, work in advantage/disadvantage.
2) Probably start level one a little less "heroic" - I liked the idea that adventurers were professionals, even at level one, but it could start a little lower.
Personally I don't mind the starting point for 1st level chars, so I'd keep this as an optional "0 level/pre-hero" rule.
3) Make magic items magical. - IMO one of 4e's biggest weaknesses was magic items - BUT I would LOVE LOVE LOVE mundane items to have a nice long range before things become magic. A "bearded axe" that gives you a chance to trip? Etc. Items could come with "powers" without having to be magic. Save the "real" magic for paragon and epic.
Aye! For starters, as part of the flatter/reworked math, forgo requiring and remove any bonus to hit on a magical weapon (similar to the inherent bonus mod, only not adding/requiring it) except in rare cases. Then, magic weapons have interesting properties: greater weapon base die, additional elemental damage dice, interesting abilities or bonuses to abilities and powers, extra powers, and etc. Similarly with armour and other items. And encourage naming items and giving them unique flair (that may or may not affect mechanics).
In addition, ensure that flavourful/creativity-inducing items remain and are highlighted: feather tokens, decanters of endless water, universal solvents, immovable rods, etc. Out of the box player thinking FTW!
(As a solution to the Christmas tree effect in 4e, our group rolled with it such that when you 'got' a magic item you could either have it be a magic item or re-fluff it as a new skill/talent/ability the character acquired, or something in between. For example, for my runecaster, getting a 'magic item' that improved their resistance to elemental magic I described it as him having been continually etching runes on his armour and now they are complete, energizing to grant them the resistance. For my ranger/fighter hybrid, a "pair of boots that lets you stand up from prone as a minor action" was just something they'd developed innately. In all cases, the mechanics didn't change, including slots and etc, in order to maintain balance, but these descriptions made our characters and the game more evocative and personal. Doubly so if you chose to keep it as an actual magic item... because then it was a MAGIC ITEM.)
Similarly, ensure and include spells and especially rituals that likewise invite creativity and non-strict-encounter use (or that only have a described mechanical effect.)
