Uhh... If you waste resources making stable defences for all the outposts you may be abandoning then you have yourself wasted resources.
And why would anyone abandon an outpost? This isn't Starcrap; resources last forever.
Now that I'm thinking of Starcrap, that has flying structures, doesn't it? If I recall correctly, however, none of the defensive structures can be relocated. The more I think about this, it sounds more like a combo between Siege Tanks and flying buildings...
And I was between laughing, crying, and groaning when I read your complaint about "rear defenses doing nothing". Be glad that they ARE sitting there doing nothing, and that you aren't getting attacked from more than one side...
Unit missions are called
UNIT MISSIONS for a reason: you have to rely on your ability to guide a small group of vehicle to achieve victory, rather than just spamming massive amounts of cheap vehicles. You don't have structures or a Structure Factory because the designers wanted to make sure you are forced to use what you are given to the best of your ability.
And as for tube benefits... Won't tubing all over the map "waste" resources (though who are you to say what is and is not a waste of resources? I'll use
MY ore the way
I want to, thank you very much)? Besides, if the whole point of this bucket of bolts is to be mobile, it should be able to run without some puny meatbag's assistance. You can't have it both ways: if it's mobile/deployable, it should get none of the "tube benefits" of the regular GP.