I think for summer alpine climbing, where you’re dealing both with heat and cold, where staying cool is crucial to staying comfortable, a layering system works best. The Montane Extreme smock is my number one go-to piece for anything cold and gnarly, where I want the maximum robustness in my clothing, as it copes better than anything else for stop and go in cold temperatures, where multiple layers would not. This is a winter exped, winter north wall piece. But for alpine climbing in mixed environments there is very little flexibility, and a lot of bulk, so you may find that you’d only find comfort in the extremes, i.e in just a base on the walk-in you’d be great, and when the weather gets bad, or you’re on the summit day, the smock would work great, but with just these two pieces, in the mid temps (mid-altitude, warm but windy) you’d either be too hot or too cold. My article on North Wall climbing is well worth reading as it’s a progressive look at a modern layering system, although gear’s moved on quite a bit since then.
I’ve just spent 2 days in the cold lab in Newcastle with Montane testing some interesting new fabrics (which involved having a thermometer stuck up my ass for 2 days!), and there’s some interesting stuff on the way. Also working with Montane on a more ‘system’ approach to clothing, integrating base and mid-layers better for stop-go stuff - but all such stuff has long lead-in times (won’t see it until 2016).
My advice would be to think about these key points:
Get clothing that gives you the greatest performance out of the smallest amount of weight and bulk.
Focus both on heat and sun protection (imagine you’re walking in a dessert) as well as apocalypse scenarios (enforced snow hole without bivy kit, looking after a static casualty).
Summer alpine climbing is a dynamic movement sport, where you need to move fast, stay light, and feel unrestricted so instead of seeing it as big beards and heavy fleeces, look more towards mountain running (look at the kit someone like Kilian Jornet uses).
Lastly, if you have to ask these questions perhaps you’re yet to have received enough lessons from the mountains to really know - or even understand the answer. Alpine peaks can and do punish the ambitious, as for every bluebird day there are many stormy days that will freeze the unprepared to the bone, and even the best do get caught out and pay the ultimate price for speed. So take my advice, but always err towards a little more until you know yourself how close to the bone you can go.