Featherlight would count as a “thin shell jacket” surely…
OP, do you want windproof and warm or waterproof and warm…? Road running close to home or out on the fells…?
Montane and Inov8 are doing some quite nice windproof, non-membrane softshell type stuff that may be of interest – Montane Mountain Star and Trail Star; Inov8 Race Elite 275 Softshell…
Personally, on the fells I tend to wear a merino blend Ron Hill Vizion long sleeve to keep warm and if there’s a bit of wind or rain then I add either a Featherlight windshirt or a Minimus waterproof as it’s a more versatile set up and avoids the boil in the bag feeling.