The concept of the REL line array is not about more bass but better bass by spreading the work to different subwoofers. If you're interested, you can hear the explanation of John Hunter CEO of REL:
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I would totally agree it's pricy and not for everybody, but it works. It's a bit of pain to set up at first but when you get there it's really great.
As for the rug I agree it would look nice, but it would not do much about sound reflection. Here's an explanation from a sound theory book:
"As a line source, the electrostatic panel maintains a consistent sound pressure level over a wide vertical window, with measurements indicating a consistent treble response over a range of ±10° relative to the panel’s midpoint. This controlled vertical directivity helps minimize strong floor and ceiling reflections, which is characteristic of electrostatic line-source transducers."
So, the only thing it would help is the low frequencies from the 12" woofer at the bottom. Unfortunately, a rug cannot stop low frequencies however thick it is. Low frequencies are standing waves between wall boundaries and are not directional. Maybe I should go fetch one from my garage and redo the picture, so people feel better for me. :-)
I agree about the Center Channel analogy. When I play stereo music to other people, the center image is so strong and precise that everybody is convinced it's coming from the center channel. On the other hand, when you switch to Multichannel music like 5.1 or Atmos then all bets are off because you are at the mercy of the mixing engineers. It's like a competition on who's going to come up with the craziest idea like putting deep bass in the center channel or even worst in the back surround. To cover all bases, if I count the 6 powered subwoofers in the ML speakers I end up with 16 subwoofers. 12 of them are always active and the other 4 only when the music requires it.