This sounds pretty much how I ran all my combats pre-3e. The only question I have is when do the monsters go once the fight has started? Just when you feel it's appropriate? Once the PCs have all done their thing?
What happens is that everyone declares their action(s) for the round, such as:
DM: The 3 giant ants are charging your henchman who fell into the hole.
PC: I am drawing my rope and throwing it down to my henchman, then pulling him out.
Henchman: He's grabbing the rope and climbing out.
All those things happen at the same time. As the PC gets out the rope and the henchman starts climbing, the ants are charging. In this case the Henchman would get some modifiers to Defence (+2 for a defensive action and +4 for being pulled 20' out of range of the ants - out of the hole). If the ants miss, either they didn't get there in time or they missed.
I like it much better than turn-based initiative. Combat feels real and chaotic. At one point I used turn-based in this system, but ditched it because it caused too many headaches.
In battle, 4E has become more of a table-top tactical board game, the battles take a long time to resolve (unless you play with a group of experienced RPG-ers that know their PCs perfectly - and even then) and the 4E mechanics have failed in several aspects to provide interesting role-playing opportunities IMO. I don't know whether I'm ready to revert back to a DM-oriented playstyle that I played for a long time - and was quite comfortable DMing - but I clearly do not think that I would refer to 4E has being the quintescence of maturity. It is clear to me now that 4E has been very, very appealing in theory, but in practice has failed to deliver. (And I've played it a lot.)
And yet, it looked so good. When I saw it, I was under the impression that they had hit the sweet spot big time.
What was lost? Well, to me, for a RPG experience to be really entertaining, it requires us to find way to put some of those story elements back into battle, to have the fighter decide that he'll push the ant into the hole without the player counting squares on the battlemap and wondering wether they'll be an OA if the ant climbs back up, etc... We need to switch back to our imaginations more, for my taste.
What is a mature gaming system? You have your idea; I don't think it coincides with mine. Maturity might well be the act of having to accept the other person's ideas (even a DM that adjudicates differently than I would); not necessarily the act of being bound to follow very strict rules that forbid you from free-forming.
The problem is that it's all at the whim of the DM.
For example, one DM states that the Ants charge while the PC is getting out the rope, hence, there is no +4 bonus to defense because the rope isn't there (or because the rope might be there, but the PC hasn't yet pulled it) before the Ants actually attack.
In your example, not only does the PC get the rope out, but he manages to throw an end to the henchmen, he manages to hang on to the other end, the henchmen manages to get a good grip, and he manages to pull the henceman significantly fast enough to give him an extra +4 to defense (which is a huge bonus). Are the Ants 200 feet away??? The DM is also giving the henchmen a +2 to defense for the defensive action of climbing whereas a different DM would give the henchmen a -2 penalty for climbing.
It's not that it's more real and chaotic, it's that the DM decides a lot of rules that normal 4E already has baked in. On a good day, the DM gives the PCs all of these actions and bonuses in the small fraction of time that the Ants charge. On a bad day (or with a different DM), the PCs only get some of the actions done in a single round, cannot react in time to manage all of these actions or the modifiers might be totally different.
Some of your rules sound strange as well. "pushing him back down into the hole gives you a +2 to AC". I have no idea the rationale behind this, especially if I miss with the attack. So as a player, I would be wondering why the heck the DM is handing out this bonus to AC for using Tide of Iron. The power doesn't give this bonus out. So regardless of whether I hit or miss, the monster gets a penalty to hit me because everything is happening at the same time and just the declaration of which attack I am using changes the outcome of the encounter, regardless of whether I hit or miss with that power. Or alternatively, if I hit I get the bonus to AC, but if I miss I don't, so we cannot necessarily adjudicate the results of the Ant's attack until we adjudicate my attack.
The +2 bonus is there because the ant's below you and you're putting your shield in his face and shoving him down. There's a situational advantage to the defender there - the ant's below him on slope of the hole.
The PC is already getting a +2 shield bonus. Why is the PC getting a second +2 bonus for his shield? If a foe were above the PC or to the left, or right, the PC would still be putting his shield in the foe's face.
Why not give the Ant a +2 bonus to hit as it surprise attacks the PC from an unexpected direction as it climbs over the shield because the PC cannot see the Ant because the PC is putting his shield in the way? What does attacking from above or below or any other direction have to do with anything?
Do you see how totally arbitrary your adjudication is? The game is abstract, but I could come up with a dozen different arbitrary reasons to put in bonuses or penalties right or left. The idea is to not do this except in the most extreme situations. That gives the game consistency.
The combat system should be equally fair for all players if their PCs have the same capabilities and do the same actions in combat, regardless of the narrative abilities of the players.
Attacking from above or below or around the crate or over the shoulder of my ally (with a reach weapon) shouldn't result in any surprise or other advantage. It's all built into the system already with the bonuses already.
There are times where the PC should get combat advantage, but those times are part of the rules. If the DM is going to add additional times or additional rules, then the DM should list those in a house rules list ahead of time so that the players know what to expect. It shouldn't be arbitrary, and on the fly, and vary from encounter to encounter. The rules should stay consistent. IMO.
Everyone's ideas are different in this regard. I do think that a game system that has simple rules that handle 95% of combat situations is better than a freeform system where the DM changes his mind from week to week.
One way to get past your issue of counting squares (which I too dislike) is to prevent players from counting squares. Move the PC along the path that the PC is moving. If you've moved too far to still get in a standard action, I'll let you know as DM.
But then, are you... gasp!... suggesting that the DM's whim might be called upon?![]()

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.