While the average front on Comet Catcher in your images are visible, there's plenty of space to flank and attack.
But shouldnt it look like this then:
Flanking is basically noob-poison.
on ccr it looks like this for good players too.
I dont know who currently claims to have the biggest penoid in BA but [PinK]_Johannes and [PinK]8D are probally average at least. And yet this "two streams of units meet in middle" image. I still think it just how the game works.
Since we're talking about a different thing now (Fronts always forming in the same places, not necessarily that there's only one narrow chokepoint)
My point is more like this:
-fronts usually form early in the game (ie coms in dsd south walk to front at start, make llt)
-front do not shift much in most games
-fronts form in a way that they divide the map in two equally large parts. Not in several islands or something. The front is usually a somewhat straight line.
A 3v3 on Talus is going to have dozens of small porced fronts constantly shifting
why should the fronts constantly shift?
They surely do not shift like ie this:
http://www.youtube.com/watch?v=QztlQ1e4oz8
The map of my choice is Talus. There won't be enough replays, but the terrain on that map forces conflict laterally.
Yes, that is another way to make it interessting, lateral conflicts. Those maps are usually my favorites ie valley of unrest, the oasis (the 8x8 with the 2 hills) and some others i forgott.
ok. so, Talus.
I think it was even the first map I used
* 
but with an old version... atm only found this one uploaded, I'll just asume it is as good as any other:
http://knorke.net23.net/battlereports/T ... g.txt.html
The red lines are drawn by me, it is where imo 2 players "collided"
To me it looks like a surprisingly straight line.
Keep in mind that is not visible what unit moving/killing was real fighting and what is just "mobbing up."
(So the "real" fronts might be even clearer, straigher)
Every offense must cross the same dangerous middle-area
To me it seems like offenses do
not cross the dangerous middle-area until the game is won. That means apart from some things (air attacks etc) it can always be predicated where fighting will take place.
Since you this also was about
skill:
Imo the most important skills in the average team game of BA are:
-start, intial buildorder
-eco
No time to write more on this but imo once you have survided the first 10 minutes and fronts are established there is not much skill needed. You just react to obvious dangers (ie bomb a guardian that threatens your HLTs) work on your fighter patrol or spam <what ever unit you need in your area>
That is enough to "swim along" with your team and the game.
*just for fun, an image from 10(or so) Talus replays, made in early 2010:

it does not hold much value though because some replays were left vs right and some were corner vs corner.