Your midlayer should be insulating, outer layer/shell should be water/wind proof and then you adjust the midlayer based on how cold it is outside. A coat like the filson mackinaw cruiser is kinda both, but you can get a lighter weight shell if you want for warmer months.

If you want to stick with filson you could get one of their tin cloth jackets. Iron and Resin also have some comparable things. Semi-traditional shells, some.of which are water resistant. Triple aught design can be another option. Their stuff tends to be slightly more technical, but they have a good few options for water resistant mid layers. Their Ronin LS has a massive sale going right now.