Thanks for the option! What size waist are you for reference?I purchased from Vado in medium, sage color. They fit more like very close fitting tights/base layer without fly. I emailed to exchange or return and did not get a reply. Due to lack of response, I will not order from them again. Another source option is https://www.farpointeog.com/store/p/farpointe-alpha-thermal-bottoms. I have not ordered anything from Farpointe Outdoor Gear.
I would prefer to have a zippered fly, but admittedly, stacking zippered fly bottoms becomes less desirable with multiple layers and have yet to find Alpha Direct pants or bottoms so configured. My idea was similar to yours to enhance warmth as needed with great breathability. I do like Alpha Direct and really like the comfort of combo AD as a mid layer ( Beyond Alpha Aura Jacket) with Brynje Super Thermo base top. Black Friday sale is over now at Beyond Clothing now, but good discounts may come again for Christmas/after Christmas sale. If you get the Timmermade, please let us know how it works out for you.