In reply to BnB:
I can't quite get the advantages or how what you're after would work?
I use a similar set-up to you, and as well as the lack of faff one of the things I really like is the lack of binding/catching between the layers, which won't happen if you put another fleece type thing on top of your base and mid-layer?
Wouldn't it be better to just get a sightly thicker base or mid-layer rather then add in another whole new layer?
In the winter I use one of a few base layers varying in thickness and design (with or without a hood) and then a hooded non-membrane softshell, a Polartec Alpha hoody, and a waterproof shell, and mix and match those three to suit, and they can all be worn on top or under each other with no problem.
In the summer I use a similar mix but with obviously lighter base layers and then a hooded pertex windshirt, a thin microfleece pullover, and a waterproof shell, and mix and match them to suit again.
On top of both those systems I carry a synthetic belay jacket (light one in summer/heavier one in winter) for emergencies and stops if needed.
What it lacks in perfection I find makes up for in lack of faff and complications.
If you really want something else, maybe a thin windproof (with maybe a very thin lining?) like you suggested?
Post edited at 07:18