Just because ideas are derived from the spatial-temporal world doesn't mean they exist within space and time. There's no reason to believe so. And, IMO, all your arguments fail for one simple reason - do ideas obey the laws of physics?
Ideas are not tangible, sorry.
Of course ideas obey the laws of physics. They only exist within our imagination bound to a world of laws of physics.
Yet I apprehend ideas without the need for physical forms.
And are you ready to bite the bullet and say that you can touch, see, smell, hear or taste ideas?
And again, your brain thinks wrong. The problem is that you trick yourself to believe that if you have the idea of yourself flying (Physically impossible in its purest natural form), you are suddenly within the grasp of something out of this world. The idea of flying is bound to this world, as flying itself is within the materialistic view of reality - difficulties to explain aside, the very idea of you being able to fly isn't abstract. You recognize birds flying and put that idea together with your own. That doesn't create some new magical nonexistant dimension that has abstract inhabitants of human thoughts. Human thoughts are bound to reality, since they derive from reality.
If an idea is omnipresent, why does your mind have the freedom to make it up? You are romantisizing the idea of the human mind, promoting that thoughts, bound to numbers and chemicals, can comprehend the zero and the infinite. Remember that no matter how big a number you can think of, you will never get near the horizontal eight. Flying is a good example of this; no, it can't be done in the physical form, but it is a physical imagination, bound to your sensations from the real world - you imagine touching, seeing, hearing, smelling, tasting. Vague sensations are
pathetic when compared to the nonexistant infinite - saying that petty human physical ideas make up the infinite aether is like saying there are angels in heaven.
If you didn't catch where we disagree, I'll note you that in
your world view, the physical world is what you sense, and the aether is what we imagine, and that the aether has makeup from reality. That just doesn't make it when realizing this world is numbers, chemicals, and that all laws are defined in some way. The aether is instead what laws this world doesn't follow, it is there while it isn't, the
actual truth of the abstract aether is that it isn't from this world, it is nonexistant while everywhere. Our mind can attemp to comprehend the idea of another plane, but we fail to realize it isn't there - or, at least, is unreachable for us since the aether isn't chaos but still is, and isn't logical by our standards.
EDIT:
Your brain can only imagine ideas that are within it's physical limitations to imagine. A deaf (deaf from birth) man cannot conjure musical ideas because he lacks the sensory organs to imagine such things.
This made it much clearer than my whole post. Thanks Narz.

xD