Is it intentional that the only way to play the game is to never let the aip be greater than the floor?
No, and that is
by far not the only way to play the game
If you're trying to
win 10/10, or possibly even 9+, then yea, you need to ride the floor. I don't see a problem with that.
On the 7-7.6 range you can get away with a couple hundred AIP before things get seriously dangerous, assuming you have a decent defensive setup. If you really crank the defenses you can probably hit 500 AIP before things get completely out of hand (non-superweapon game).
FWIW, I certainly don't ride the AIP floor when I play.
On the question of what difficulty to balance around: 7, 7.3, and 7.6. Anything lower is intentionally for a low(er)-challenge game, anything higher is getting into the "so I hear you liek to suffer?" range. The fact that the suffer range is so large is reflective of the people I tend to hear from
But the 7-7.6 range is very much the focus in that if there is anything seriously wrong with the balance on those difficulties that takes definite priority over the others (though if 1-6 got really hard for some reason that'd be important to fix too, for the sake of new players).
But I haven't been hearing complaints about 7-7.6 being too hard or too easy lately
I
have been getting complaints about 10/10, largely due to my meddling with it earlier this year to remove some artificial "it kills you in the first 15 minutes, but if you survive it's actually a lot easier than that" problems. I think 10/10 is actually fairly close at this point (in the next version) to where it needs to be, though I'm sure our resident cheesemasters will find some way of breaking that illusion