I dont think that this solution is going to do what you want. Lets pull out the calculator for a moment.
Lets say you decided to use 12V as you in-wall wiring standard, which would be fine (possibly) for the low voltage equipment you are running. But in order for a computer (200W approx) to run it would mean 17A of current which is approximately what current wall wiring will carry (at 240 VAC home circuits are fused at 10-30A), but you are running the wiring at maximum capacity which isn't a good idea. If you wanted to run a heater (2000W) that would mean 170A of current, which would require large impractical, expensive bus bars in the wall.
You could try increasing the voltage (say 120VDC) and this would mean that all the current wires would be ok, but you still require wall-warts for your devices, most phones run on 3-9V so require this voltage to charge, so you still require DC-DC converters, the only part you would be removing would be the rectifier. Also the danger would increase because as I understand (no experience with this sorry) if you held a high voltage DC line your muscles would grip and you can't let go, but with AC, because there is a zero crossing then you are able to release.
Finally, you could possibly run 2 sets of wiring, one as low voltage DC and one as high voltage AC but this increases the overall cost, and you sitll would need to determine which DC voltage would work best, otherwise electronic stuff would still require DC-DC power supplies.