I agree with KBentley57 that 60 degrees is too great a temperature swing for "zipless" solutions, and with other posters about the unsatisfactory properties of cotton jeans. In temps below 25F, I wear mostly the same layers I wear for back-country skiing:
- merino wool underwear
- breathable, windproof and water resistant soft-shell jacket and pants, preferably Schoeller fabric.
- add hard-shell jacket if really windy and/or temps below 15F, and sub in a down sweater when temps below 5F.

My comfy wool work pants and belt hang in the office coat closet, with 5 minute change-over at start and finish of the work day.