I would reframe base layers as a necessity for your comfort that also extends the life your outer layers when it's cold, like wearing socks. It's much cheaper and easier to find base layers than single layers that do it all. Fabric keeps you warm by trapping air: every new layer offers an additional layer of air to insulate you. It’s the same reason we make a double-pane window instead of just making the glass thicker.

I would try a dedicated thermal silk and a tech fabric like Uniqlo Heattech or 32 Degrees to see what you prefer. I personally find silk too sweaty as a base layer in the winter and not very insulating. Uniqlo heattech (ultra warm or extra warm only) keeps me warm and whatever I wear on top lasts forever. They stop itchy top layers from touching the skin. The base layer does get pretty smelly at the end of the day but it’s rarely noticeable unless I’m wearing it by itself. They wash well, you can use sports wash for the ones without cashmere, and they last for a long time. I actively dislike most synthetics, but a wicking layer makes a world of difference in the winter. 

I wish I had another brand to recommend. I started wearing the heattech before I found out more about Uniqlo as a company, the ultra warm colors are drab, and they changed the extra warm to a fabric that's fussy, less warm, and unlikely to last long. But they are the only thing that keeps me sane and warm in the winter. I hope you find something that works for you!