It has always been my understanding (but have no way of really backing it up by rules or regulations), that the area under the nose (the obscured segment) is already accounted for.
The EU-OPS requirement is that (a.o.) "A 90 m visual segment is available from the cockpit at the start of the take-off run". To me, this means that you have to be able to actually see 90m from the cockpit - and the only way to be sure of that is seeing 7 lights (6 x 15m).
This would also make sense of the difference between the requirement for an RVR of 125m (CAT A/B/C) or 150m (CAT D), and the required visual segment of 90m. The difference (35m resp. 60m) would serve to account for (an approximation of) the obscured segment.