I've always had difficulty in choosing the right layer to go over my base layer and under my rain or wind jacket, particularly early in the morning. When I crawl out of my tent and the weather is what I would call, neither hot nor cold, I then try to find the warmth level that I like as soon as possible.
I've often found it too chilly to stand around wearing just a base layer, and for example, a shirt on top, so I've often looked for a fleece or something similar to wear as well, just to warm me up by a couple of degrees.
The nearest I've got to a 'jack of all trades' garment is my Alpkit synthetic 'warm' full-zip jacket, it's thin(ish) so I don't use it a lot, just to warm me up by a couple of degrees when needed, or if I want it to warm myself up by a few more degrees I'll then wear it under my wind jacket.
The other time of the day, after hiking for hours when I can feel a similar chilliness is in the late afternoon. If I stop for a rest for example I may then feel a bit cold so I just slip my Alpkit jacket on, it usually does the trick to get my body heat back to the temperature that I find to be comfortable. I've tried fleece's (I have two of them) but after a few minutes of pottering around, I find they start to feel a bit clammy and will make me hotter than I want to be.
I may sound picky but getting up in the morning and maintaining a stable 'feel-good' temperature is an experience that I like.
I know that my Alpkit jacket does the trick, but I've never been able to work out why it works in the way that it does. If I could understand why this jacket works in the way that it does I could then hopefully purchase something that will also work in the same way?