If I have to run an entire team, I have no downtime. In global playing 3 powers, I’m active pretty much nonstop for 10 hours. In tournaments, you won’t see any downtime at all–some players like Steve play in the Classic and 42.2 tournaments AT THE SAME TIME, BACK TO BACK!
Its only when you have multiple players that this is an issue, and some of it comes down to needing to change player behavior slightly in order to add efficiency.
Starting imm. after I place my team’s reinforcements, I lay out new pieces to reflect what I think I’d likely buy the next turn. This may change completely based on new information, but there is never a time when i’m sitting chatting or on my phone when I could be considering my buys and combats for the next round (and beyond). I also recite everything I bought, with the math, so as to avoid mistakes.
When its not my turn, I’m cleaning up, chipping up, reviewing my own actions and those of the other players in order to make sure nothing was skipped or done incorrectly.
Rolling takes alot of time and logistics. The players who are rolling are focused on getting dice and manipulating them; the other players should be 1) counting casualties 2) reciting what’s being rolled to all so that there are no mistakes being made 3) helping clean off the casualties/rechipping on behalf of the other players. In other words, acting like a croupier.
If you are talking about editing entire parts of the game, we just discussed over in the AAZ section how the designers have already moved the “purchase, place” steps to the end. Some players have suggested its just as easy to put the collect income piece in that sequence as well, replacing 3 steps with 1. The method you suggest of simultaneous turns tends to create alot of confusion when its time to do the moves where the players on the same team act in tandem–the first moving player gets to decide where his attacks are best used, the second always mops up what remains to be done. The rules that govern the second player will be different (landing airplanes, moving through straits).
It may just be me personally, but I’m rarely bored playing AxA, any version. This is because I’m always actively involved in the game (logistics of set/up, clean up, narrating the turns of other players, reviewing their actions, also getting food/beer/bathroom). After 25 years of gaming experience, I believe that there is always something to do that can move the game forward–such as arriving early to set up even if the other players cant, watching a tutorial/research before hand if i dont know an answer, providing food, etc.
In brief, I don’t think modding the conduct or rules of the game is the low hanging fruit here. The most time is wasted while players think they are waiting on someone else, not considering what can be done to move the game forward, and being distracted/distracting. Someone constant needs to “proctor” the game–saying “Is it my turn? Who’s turn is it? Where are we at?”, which is why I like to narrate most of the action myself.
You may regard my approach as neurotic, but I run (lead) quite a few game clubs (euro, pathfinder, magic, star wars x wing, axis and allies, wargaming) and these rules essentially apply to all of them–I’m taking the reigns + an active role to ensure everyone has a good time.