A bit late but for this thread however...I think the idea of the SBS having both L & N busbars for the RCBOs is terrific!
But the need to sign up and the niggling concern that in 5-10 years they are unavailable would bother me a little. I guess they are made by some major company to specification, but without knowing how much spares will continue that might count for nothing. Same with a few of the own-brand or similar CUs, they might have identical MCB/RCBO from big names, but the hassle of justifying it for a future fix should the original brand have vanished / been phased out as unprofitable / etc makes me personally stick to the big-name brands if I can.