In reply to london_huddy:
I would agree, although it depends on the weather and the route. Used Cioch sallopettes for all alpine routes for years, but don't any longer. Great when caught out high on the Kuffner arete (snow showers and an unplanned bivi). However, too warm for 90% of the time once the sun is up. Got a photo of me in cloud on Matterhorn summit in said salopettes (vented), and just a baselayer (unzipped). Having said that, every time I see Alan Kimber in the alps he seems to have his Velez smock on!
My suggestion for the Matterhorn, assuming good weather, is to treat it as a 1200m scramble, akin to 2xTower Ridges. You'll be aiming to be moving as fast as you can for 6 hours and it is a late start from the hut, so you are only doing 30mins in the dark (owing to routefinding challenges) After a baselayer, my choices would be (1) microfleece/powerstretch + windshirt or (2) softshell. Emergency layers are normally (1) light waterproof and (2) synthetic or down overlayer.
If you are really worried/cautious, you could use the weight saved by not taking the paramo to add a (bigger) bothy bag. If you end up sitting somewhere, a shelter will be nicer than a big jacket. Paramo is really designed to be on all day, not carried.