In reply to HeMa:
> Well, half ropes are tested indevidually, just like single ropes (but with a smaller weight).And quite often on wondering lines, a fall is held only on one of the half ropes. This considering the fact that for scrambles, you are rather unlikely to take a huge lob in air (as you'll hit a ledge way before that), half ropes should be more than enough...
To a certain extent I agree with you, but you also have to factor in the following:
You'll often use rock features as belays/protection, which inevitably means more abrasion and chance of cutting. A thicker rope is less likely to fail and will last longer.
Quick belays and body belays are common, a thicker rope will be easier to hold.
You may not take huge falls, but the fall factor may end up being quite high if the rope has been woven around rock features and pinnacles causing drag.
For these reasons, I suggest a compromise, which is to opt for a thin single rope rather than one strand of a half rope. Many ropes in this bracket (9mm or close) are multi-rated anyway. The Beal "Scrambler" rope mentioned above was my idea back when I worked for Lyon, it seemed perfect to use a 9.1mm single rope as the weight penalty was minor yet the rope felt more reassuring when weaving the rope around pinnacles and using direct belays.