Alternate Turn Sequencing?

[Lord Mayhem]

I was idly considering the who issue of turn sequencing (how does the game structure work) and the issue of who gets first turn as a game balance issue, and started wondering how would alternative turn structures work in 40K, as a thought experiment.
Background:
In general the “who goes first” roll is one of the most significant one in the game (though the “steal the initiative” roll probably has more emotional impact  ). Knowing (to 85% accuracy) that you are first or second directly influences deployment strategies, and can provide advantages in taking objectives, seizing key terrain and eliminating enemy forces, before they can do anything (especially if they rely on Psychic defences). Obviously terrain, skill, and luck can influence it, but going first can provide a significant advantage. One of the old offsets, last turn moves to seize objectives is now a huge gamble due to the random gamelength.
Game turn structure can be done in a number of ways; generally divided into movement and action phases (40K goes with a move-action-move/action setup). The biggest variant is how the alternation between players occurs. For notation I will use M and A for Movement and Action phases (generalizing here) and 1 and 2 for the players. Army means all units act together in each phase, Unit means individual units act per phase.
So by this 40K uses a Army M1-A1-A1/ M2-A2-A2 structure. (yes, everyone knows this, but it serves as a notation demonstrator)
Common alternatives include Individual M1-A1-A1/ M2-A2-A2, and Army or Unit M1/M2-A1/A2-A1/A2 (ie all movement is done by both sides before actions occur)
Hypothesis/Discussion:
What if 40K instead used an Army M1/M2-A1/A2 structure? (side A moves, Side B moves, Side A shoots, etc) I considered Unit systems, but feel they become unwieldy at 40K battle sizes, and Joining units gets complicated.
So player A wins first turn, and moves all his units. Player B then moves all his units in response, repeat for all other phases (in the assault phase Player A conducts all charges, then Player B, then fights are resolved).
This would create a more fluid battlefield as player B can react to Player A movement before being shot, allowing him to reposition to reduce the effects of an alpha strike. Player A still has the advantage of having the initiative for maneuver (potentially driving Player Bs maneuver options), and still shoots first, but now Player Bs movements have to consider Player As shooting , and Player As shooting has to allow for Player Bs movement ( whereas now each player can maneuver with an expectation that shooting will allow for a more advantageous position before the enemy can respond. Similarly, you’ve already received their shooting, so the choice of moving or not is less influenced by immediate threats)
My own speculation is that this would make for a more mobile and faster game, with more tactical decision making, though several special rules would need reworking, and Army balance might need revisiting. Assault would appear to be harder to pull off (as potential assaultees could react by moving away), so moving charges up in the turn order would seem a logical choice (Like Fantasy; charge during the Movement phase, fight after shooting). Overwatch should be adjusted. If the charge moved to movement phase, Overwatch would also move, then a unit that fires overwatch would only fire snapshots in the shooting phase (if the charge fails) and/or could only shoot at the assault unit (Still trying not to get assaulted!)
Move Shoot Move Units (Eldar Jetbikes, XV-8s etc) would need reworking to reflect their ability to avoid return fire; some sort of evade option, similar to Warp Spiders would seem appropriate(maybe with an I test); if not used they can make a normal “assault move” at the end of shooting.
I’m suspecting that several “continuing effects” could be tidied up with this system, but have not yet looked into it.
Sub Variant Option: split shooting phase into 2 sub phases: units that don’t move shoot before units that do. This would allow for “fire and maneuver” tactics where one unit provides cover for another maneuvering unit. (Similar effects could be achieved by giving stationary units pinning, or -1BS while moving-it’s hard to aim when you’re sprinting to your next position) Would be more realistic, but slows down the game, so probably not worth it as more than an idle thought.
Opinions or extrapolation? What rules would need most tweaking? How do you think your army would be affected?
I’m kind of considering working this into a full “overhaul” just to see how it would work out.

[grimmas]

I think this would be rather interesting it's broadly how Space Marine used to work. I feel the current rule set wouldn't need much tweeking (even jet pack/bikes which will pretty much have the same affect). It would add quite a lot of manoeuvre and counter manoeuvre and make turns much longer but you only play half as many. It's definitely worth a practice game just to see how it would go

For clarity's sake I'm referring to a straight up M1-M2/S1-S2/A1-A2 system anything extra could make things a bit too cumbersome

[henrythesecond]

I think it's a great idea to experiment with the 40k ruleset to try and find something that fits your tastes. I believe that's what GW have always tried to encourage with their games.

How about each player selecting which order he plays his phases in? It would certainly ramp-up the tactical decision making. Shall I take my Move Phase first, to get this unit out of danger? But then I risk losing the good Shooting opportunity I have against that side armour if my opponent Moves before I Shoot...

Obviously, I've given no thought at all to how various USR would work, but that'll be half the fun, I guess.

Just my 2p worth.

[Cactus]

I like how Bolt Action does it:

Each unit gets a die. (Each army has single colored dice.)
Both players put all of their dice in a bag.
Once play begins, a random die is pulled from the bag and the player's who die is drawn, gets to pick a unit and activate it. You can move (or assault), move and shoot, run, go down for more cover, rally or go into ambush (and save your action for later.)

It's a great system, especially later in the game when you really to make some canny decisions on which unit needs to act.

[Katharon]

I like how Bolt Action does it:

Each unit gets a die. (Each army has single colored dice.)
Both players put all of their dice in a bag.
Once play begins, a random die is pulled from the bag and the player's who die is drawn, gets to pick a unit and activate it. You can move (or assault), move and shoot, run, go down for more cover, rally or go into ambush (and save your action for later.)

It's a great system, especially later in the game when you really to make some canny decisions on which unit needs to act.

Bolt Action's is one of the best in this kind of functionality in my opinion. It might actually be cool to test out 40K using this model.

[Path Walker]

Bolt Action's is one of the best in this kind of functionality in my opinion. It might actually be cool to test out 40K using this model.

Which is pretty much Beyond The Gates on Antares

[Brent]

My buddies and I have changed the turn sequence pretty substantially to try to better approximate the simultaneous action of a real battle.
At the beginning of the movement phase, we roll off; the winner gets to choose to move first or last. Both players then alternate moving their models.
In the shooting phase, we again roll off, and both players alternate any running moves they want. Then one player does all his shooting, rolling to hit and to wound; the other player does the same. Once all units have fired, both players make their saves.
In the assault phase, we again roll off, and then make assault moves in alternating order.
But I like the random element that Bolt Action uses, maybe we'll try that.

[grimmas]

Of course you could try going Battletech, alternate move units between each player and have a simultaneous shooting phase where casualties aren't removed till the end of the phase. For the assault phase alternate charging units between the players and resolve combats as normal. Have a roll off to see who moves the first unit.

I do mean a notionally simultaneous shooting phase where you resolve both players shooting attacks but casualties don't take effect till the end of the phase.