What do you mean by hard coded action enconomy. Are you advocating a Hackmaster style initiative systeM.
I don't know the HM system.
My issue is the entire 3.X/PF/4/5E system
Cyclic initiative
Round length of 6 seconds
Nearly everything tied to "until your next turn"
Hard codified categories-Actions, bonus actions, reactions, move, etc.
If you deviate from this by utilizing a round by round init- you screw up half of the monster abilities or the player's. I cast a spell, it's effect lasts until your next turn- then you roll highest initiative, and go. Now the effect ends possibly before it had any real effect. The next time, it may end up working twice as good. In T/OSR games, most things last a number of rounds, not "until your next turn" and the system is designed around "rounds".
The 6 second round also kills it for me-I've used this example before, but years ago I had one of my kid players (who was not particularly creative) come up with a fun, cinematic, dramatic attack move. Unfortunately it did not fit whatsoever into the "action system" and I had to nix it. In pre WOTC D&D games I simply could have said, no problem, called for one or at most two rolls and adjudicated the whole thing, and whether the kid rolled great or poorly, the character could theoretically have done everything including the amount of movement during the course of a one minute combat round- heck even 30 seconds, Instead it ended up being a big downer as I explained how it wasn't possible using these rules.
@atanakar Yes, I'm saying group initiative, rolled round by round. The 5E side variant does not roll round by round, only once at the beginning of combat.
@Nebulous - The BEST cyclic initiative I have found is the system from FFG Star Wars- where players all roll, and get a "player slot" on the numbers they roll- In what order they go is up to the players when a player initiative slot comes up- this way they can coordinate moves/attacks.
Frankly, I prefer Dungeon World over it all- No initiative, no rounds, all taken care of in the fiction, But obviously no workie with D&D.