This is why a lot of our children are becoming stupid these days. We're already getting less for more with the DLC, we don't need less for more in the core game.
However, I will say that you're onto something with the vault space idea. If they split the vault into more sections containing the same number of spaces per section as they have now, that would be phenomenal.
They could have primary, secondary, heavy, armor, mats, misc, etc. all separated into different sections which in turn would not only give you more space, but more organization as well. I approve of something similar to that.
-_-
What you're suggesting is for Bungie to change part of the core game (same amount of marks for less mats). I don't know how you failed to realize what I meant. Ah well, my statement still stands.