I haven't given it much thought...but at the very least there should be some kind of game mechanic or facet of the design which would prohibit the hordes from just ignoring each other while they attack scantly defended bases...perhaps smaller maps to go with the newly diminished player base, with unavoidable action packed choke points!
Easy to say, but as Lusche mentioned, one implementation of that kind of scenario failed spectacularly. I wasn't there for it, but from what I've read on the forums, blood flowed freely from the monitors of the players, brimstone fell from the skies... the oceans boiled... etc.
In my opinion there isn't anything inherently wrong (in online gaming in general) with bands of lower skilled players banding together to acheive something for once, i,.e. hordeing or 'zerging', as long as you get some fun gameplay from it (i.e. killing 40+ man groups with 8 guys in the old fantasy mmo DAoC
)
We're on the same page there. My game sessions pretty much revolve around defending a front somewhere.
In fact, two large groups of planes clashing sounds like a jolly good time to me. The problem is that there is nothing pushing players in this direction (the direction of action, competition and in my opinion, fun)...
That's the fight I am ideally looking for. Big red bardar vs big green bardar. I come in high and look for red guys doing the same thing. Fun for all.
It's too easy to just avoid combat or any kind of test of skill all together, and that to me speaks of poor game design - unless of course you are designing a game for the kind of people that play WoW pve and stuff like that...
...come to think of it a lot of the AH player base probably does fit into that kind of category (casual, non-competitive), just with added aviation enthusiasm...so perhaps the problem is that two different breeds of flight sim pilot are being forced into the same arena? Thoughts? 
This is something I have believed for quite some time as well. A lot of people don't look at an online game as something to play for the challenge. Instead, they're looking for something to take the easiest path through to victory. They're basically applying PvE tactics to a PvP environment, and gameplay suffers for it.
One of my favorite things about this game is also what I think causes the main problems. There is no facility to 'balance' things. If the other side sets itself up right, you can wind up in a truly unwinnable situation through no fault of your own.
What I find fun is trying to find a way to prevail against whatever setup they have thrown at me. Large numbers inbound? Up from the next base over in something fast and work the edges of the crowd/go for the highest value targets, like bombers or goons.
The way I see it, the gameplay you get in a large, unrestricted open arena where people can basically do what they like is what we get every day in here. The path of least resistance is sought by the majority, and followed through on. The only 'goal' for goal oriented people to fasten onto is winning the war.
Unfortunately, the most effective way to do this is to roll undefended bases as quickly as possible. Anything people do other than that is only slowing your side down. If one of the other countries is doing the same thing, it is faster to let them take one of your bases and roll it undefended later, than it is to defend it. About the only time defense works to help your side is if relatively few of your people can actually stop a rolling horde cold. That doesn't happen very often.
I can't think of a system of gameplay that retains the open world concept that can get around this. In fact, I believe it is by its very nature what you get with unrestricted side-based combat.
What it seems to me would give a lot of people what they want is some kind of goal-based small arena setup almost like Counterstrike, where you've got a map, and 16 or 32 players on a side, and a time limited goal like capture the field, or defend the bombers through to bomb the airfield, or what have you. It would be a fair fight, people would be assigned sides to ensure numbers, and they'd have some kind of 'bite sized' fun.
If you look to the left, there are custom arenas available that could do just this. Nobody seems to want to set it up and run it. This kind of gameplay is... what's a good word... painful to me. I would rather play pattycake with a grizzly bear than fly in an arena with that much restriction.
People often believe a graphics update is what will fix the game. Graphics upgrades are swell and all, but if the core gameplay doesn't change, how does it extend the life of the game? Fighting in the main arena, you're still doing the same things regardless of how pretty the smoke looks.
It will also shut down a good portion of the client base who aren't running decent rigs. I agree with some of what Rich52 says in his post, but being able to afford internet is one thing. Being able to upgrade your PC to run a game with more modern graphics is another.
And frankly I find the Hitech crowd to be a little to much on the arrogant and elitest side. They take their customers for granted.
About the only criticism I would levy against them is they perhaps don't sugarcoat their disagreement with the playerbase. I personally find it quite refreshing when someone posts a bad idea and gets the response 'That is a bad idea.' Not every idea is valid, or practical. Another thing that quite often happens is, they get a wish for 'something to improve the game' that nobody can adequately define.
They make their choices, and live with them. If an example of a company that doesn't subscribe to that train of thought is desired, take a good look at SOE's MMO division. In particular, take a look at the history of Star Wars Galaxies. Bask in the horror of design by committee.
Wiley.