Ignoring that you just wrote a treatise on how to deal with it...and same damn fine suggestions I might add...you kind of proved my point.
Not really (but thanks for the compliments!).
The "complicated" stuff happens at prep time - having good notes done beforehand is all that's really needed, and that will be true regardless of how many players you're running for.
I use initiative cards regardless of how many players I have, so that's not a change required for large groups; it just makes large groups easier to manage.
I am at a point where I can make up relatively balanced monsters stats for a given level of PCs, so I can wing a combat if I need to - but new DMs aren't at that point, yet, so they'll need to do the prep work anyway.
It certainly sounds like some DM's have a better handle on large squad combat than others, but my point is not whether the DM can handle it, but will players get bored between their chances to roll a die...miss..and then wait some more.
This part makes less sense to me.
I am proposing a combat with, essentially, badguys equal to the number of PCs. By doing so, I have reduced the number of and the complexity of the decisions that the DM will be making, vastly speeding up his turns.
Additionally, I am doing so by making "big monsters" which have [largely] the offense and defense of "little monsters," meaning that PCs will not be missing quite as often. Additionally, doing so allows those Power Attacking-brutes the chance to pump some attack bonus into damage and still hit reasonably well, while at the same time reducing their ability to quickly end a combat (because of the higher chances for "wasted damage").
This avoids the chief problems attendant to using a smaller number of tougher monsters: 1) that unless you're really careful, you'll end up with monsters who have defenses that the PCs cannot yet overcome, and attacks against which the PCs cannot adequately defend, because the monster is designed around fighting characters two or three levels higher; and 2) the action economy favors the team with more actions, leading to PCs being able to dogpile a small number of relatively more powerful monsters and steamroll them, resulting in anti-climactic fights.
But a question, in large groups, 5-8, do people find that one or two people still try to or end up running all the combat manuevers? I find the women in our group couldn't care less about the tactical game. They are happy to roll dice, but they leave all the tactical stuff to the others.
Quite the contrary, in my experience.
In the "social" and "exploration" side of things, it's really, really easy to have the party follow the lead of one or a few characters. This goes double for large groups, where long chats about which way to go in a dungeon just slows things down even more.
Unlike social and exploration, though, the D&D rules have a built-in baseline of combat effectiveness. It's possible to build a character who has almost nothing to add to a social scene (consider most Fighters, for instance), while it is nearly impossible to create a character with no combat ability. In my current Pathfinder game, ferinstance, we've got a player playing a rogue who is almost completely spec'd away from combat; he's a dedicated "face." And yet, even he attacks at +5 for 1d4+2d6-1 damage when he's flanking.
Accordingly, combat encounters are almost where it is easiest while playing D&D to get everyone involved.
And as far as the sex of your players, in my group the three women are playing a Barbarian, a Paladin, and a Fighter, and are the ones most likely to push for more combat.
