The game needs to be viewed as an ecosystem, and despite the demands of one group within that ecosystem its the tension between the ecosystem that enables it to thrive. Too much on base taking, everyone else gets frustrated and leaves, too much on air combat, base takers/gvers/etc.. leave. I have in the past have expressed frustration with the hordes taking bases, etc... but I have come to the realization that they are as important as any other group, the key is balance.
Much like the balance in the ecosystem of 'roles' there needs to be a balance in the effect that they can have on the 'objective', whatever that objective may be. One can easly notice that the land grabbers only have one target which only has at best marginal impact, which is taking bases. Maybe a more complex strat system with more targets other than bases would foster more reward for the success of their efforts. Also, this would also encourage others to care about being attacked. Furthermore, this would enable newer players to feel 'accomplished', and ultimately thats what makes the game for all of us, 'Horray I did it!', whatever 'it' is.
More complex could mean, maps, that have obvious choke points, via the use of rivers which can only be crossed at certain points. Another idea is to have items like factories have a more noticeable impact. For example, today bombing a fuel factory only limits the rebuilding of fuel sources at bases. If it instead directly impacted the amount of fuel you could take in your plane and this combined with a map where most bases were not 1/2 a sector apart, then people might care.
Another idea, is to have a more explicit concept of a 'front' where you can't spawn a GV beyond (or some other limitation). This front is moved forward by the acquisition of marked strategic points such as the top of a hill or a bridge at a river, or some level of air superiority. This would add more of an objective to the game while hopefully enabling some intense fights.
These are all just crude ideas and I'm sure many better ideas will surface, but hopefully its a starting point.