In reply to rss91:
What you choose to purchase, borrow or even hire depends on what other, if any, climbing you intend to do. So it is hard to answer your question without a profile to refer to. If you are only likely to do Mont Blanc or something similar this once I suggest you borrow or hire a warmer down jacket if you can.
However, here are some thoughts:
Baselayer:
Personally I find Merino 200g too warm for alpine summer including 4,000 metre peaks. I would normally wear a synthetic baselayer ( wicks more efficiently than Merino ) that has long sleeves I can roll up, thumb loops and a deep chest zip for venting. In my opinion it covers a wider range of likely temperatures. Great on it's own on walk ins, wicks very efficiently and other layers provide the insulation.
I've climbed many alpine 4,000 metre peaks in the summer months and have never needed or used a base layer on the legs. I personally would get too hot and removing them would be a faff. Lightweight softshell trousers are fine most of the time and, should it get cold, lightweight full length zip overtrousers can be put on for the night time start or if very windy / cold and can be removed very quickly and easily when the sun is up or the wind stops.
Mid layer:
Personally I find a lightweight softshell jacket (with a hood) is lighter, more packable and versatile than a fleece. I have done Mont Blanc with the baselayer mentioned above and a light softshell. However, other times I've needed to add a much warmer layer or two.
Outer / insulating layer:
You might get away with using the Ghost Whisperer as long as the shell jacket can go over the top of everything - you may not need to wear it at all but absolutely must take a really good insulating layer. As others have said, it can be damned cold and exposed to wind for long sections. Personally I would take a medium weight synthetic or down belay type windproof jacket that goes over everything. I use synthetic because it suits my other climbing better but down works really well on Mont Blanc. I rarely carry a hardshell top in the alps for a day route, but may if the forecast is dubious or I'm high for several days and the weather could change. Mont Blanc is not one to do in a dubious forecast! I don't know if you are with a guide or not, if not make sure you know the signs of impending worsening weather on Mont Blanc and seek shelter / turn around sooner rather than later. Depending which route you do losing height quickly is not easy.
However, since you've already purchased the Ghost whisperer you may find a lightweight down gilet or jacket that can go over the softshell and act as an extra midlayer boost would work. Your ghost whisperer then can go over the top of that if required.
Several people have mentioned the benefits of hoods. I find a lightweight hooded softshell with the hood on the belay jacket ( both must be helmet compatible ) are usually fine. I will sometimes carry a very thin hat or balaclava that can go under the helmet if the forecast indicates it is going to be very cold. However, for many parts of the route where I don't need to wear a helmet or hood a peaked lightweight sunhat can be very useful. So I wouldn't get a hood on the extra mid layer - too many hoods!
A pair of thin or medium thickness windproof gloves plus a spare pair are usually fine. Have an extra pair of thick gloves or preferably mittens that can go over the top in case it is very cold.
Although the categories are not as clear cut as you might think I suggest you hire B2 boots rather than B3. More importantly, make sure you get a comfortable pair that suit your feet and wear them as much as possible before doing MB. Loads of places hire out boots in Cham ( if that is your base ). I would suggest medium weight socks that you have already used and you know are comfortable. Thick socks will be too hot on the approach - if doing the Gouter Route, and your boots should have good insulation too. Take two pairs of socks. If doing the Gouter you could wear one pair on the approach, switch to a dry clean pair for the summit day.
Gaiters can be useful but often not necessary. Very small / lightweight gaiters are fine.
Hope this helps