Initial reactions:
This reminds me of a variant initiative system from Len Lakofka's Leomund's Tiny Hut column in The Dragon, that was very popular in my area (I used something like it for a decade), but not so much of AD&D's actual initiative system (aside from being complicated and inconsistent, that is).  
Maybe I'm not remembering the official one in enough detail?
	
	
		
		
			Initiative	Dice
Die Action
d4 Ranged	attack
d6 Movement
Swap	gear
Any	other	action
d8 Melee	attack
		
		
	 
Still seems you can draw, knock, pull, and loose an arrow before an adjacent enemy can hit you in the face, fairly consistently.  Maybe if you're Legolas.  
 
  
It's bad enough ranged attacks don't draw AoOs (among other things).  
Weird.
	
	
		
		
			Multiple	Actions. If	an	effect	grants	you	an	
additional	action	without	the	use	of	a	bonus	
action,	you	roll	an	initiative	die	for	only	one	of	
your	actions.	Use	the	largest	die	that	
corresponds	to	any	one	of the	actions	you	plan	to	
take.
		
		
	 
 If the system addresses extra attacks anywhere else, I missed it.  Apparently attacking two or more times is somehow /not/ attacking any faster.  At least it's not attacking /slower/, like bonus actions apparently are.
What about Extra Attack, or at least Action Surge, reducing your initiative for the first attack/action? 
For instance, when you Action Surge you roll your initiative, take one action at 1/2 the result, and the second normally.
	
	
		
		
			Delaying. You	cannot	use	the	Ready	action
under	these	rules,	but	you	can	instead	choose	to	
delay	your	turn.	Instead	of	taking	your	turn on	
your	initiative	count,	you	simply	act	on	a	later	
initiative	count,	before	or	after	other	creatures	
as	you	choose.	I
		
		
	 
 That's generous.  
I'd think if you're genuinely dithering, you shouldn't roll initiative until you decide what you do, then, on the count you make that decision, roll initiative and add it to the current count.  
I think Ready could work, too.  When rolling initiative, state the specific action you're readying.  If you beat the initiative of the creature who triggers the ready, you can use your Reaction to interrupt it or just take your action right after it finishes (but still have your Reaction).  If it beats you, you don't get to take the readied action.
Edit:  I feel like there needs to be a 'too slow' rule, like if you do too much and roll too high there's a threshold where your action rolls over into the next round.  
	
	
		
		
			Variant:	Spell	Disruption
For	added	AD&D	flavor,	you	can	introduce	the	spell	
disruption	rule.	Under	this	rule,	if	a	creature	that	wants	
to	cast	a	spell	takes	damage	during	the	round	before	it	
can	act,	it	is	restricted	to	casting	cantrips	on	its	turn.
		
		
	 
 Wow, that is weak.  And double-dog-optional-variant-optional.  I guess putting casters at any kind of disadvantage is all but unthinkable.  
For Added D&D flavor, maybe add the level of the slot to the die roll, and if you're hit 'between' the die roll and the level modifier, the spell is spoiled and the slot lost.  (At least, I think that's pretty close to one of the two conflicting AD&D casting-in-melee rules...)