Erm, is that list supposed to be good for 3+ seasons? Seems a decent summer hiking kit minimalist though. Though its not even good for summer as the parka is mighty light IMO unless you are restricting yourself to low elevations only. There have been many a night in the summer out here in the PNW that I have been very glad for my Down 1lb jacket along with my Montbell micropuff jacket with hood. The parka won't breath all that well compared to fleece and a windshell or even the micropuff or equivalent and will build up sweat. I know, says breathable. They aren't and never have been. Its why everyone gets a windshirt. Put over fleece baselayer as it turns wind and lets one vent far better than any softshell. If you want a no-compromise 3 season kit...
What are you counting as worn? Am I blind and am missing something obvious? Like a slap upside my head?
I have hiked in the ol' PNW, backpacked, mountainclimbed, and have never carried a water filter. I can count only a few times that I have ever even boiled water let alone used iodine drops or equivelent. You can always find water in the PNW with some forethought. Though Oregon this can be difficult along with Idaho. You can get an inline gravity fed water filter like ULA sells, weighing far less. The cascades or Olympics or coast range? Water is everywhere, just don't take it from below where people typically move/camp, and don't take water from lakes. IE if a trail switchbacks through the creeklet above, don't take water from there. Only take water from well above the trail in case things like dogs/horses/humans did their thing on the uphill side of the trail.
As for early fall, into October, seems "ok" for your list, late fall? Not a chance, let alone spring or winter. Ok, late spring you are probably pushing it as you will be on snow, but it is possible, though VERY cold. I wouldn't but its your life.
I don't mean to rain on your parade, but there is no way I would allow someone outfitted so minimally as you are to go hiking on snow with me with temps in the single digits for say a 3 day trek in late october early november or even April. Its a good start, but I see several pieces missing. Now if we knew weather ahead of time and said we would just get out of dodge if the weather turns, then maybe with that list. But this means you are pretty much a fair weather ONLY hiker. Oh, wait that is me generally as I am a local and get to look at the weather and decide if I want to go. Though, sometimes I get cabin fever and just GO!
Add 2nd set of thin gloves(forget if you had this on your list), as your super light gloves shown won't do for more than a little while, certainly not days, better ground protection, IE NOT a ridgerest that captures condensation in its "ridges" and then proceeds to soak your BBAG, get closed cell foam flat sheet sold at say Promountain sports etc, gaitors!, VB socks, insulating piece like the one you have listed times 2. 1 to wear 1 to put on for bed or trade out for camp. Do you have a windshirt in there? Layers, layers, layers... late fall early spring seems I am always taking layers off and on to stay cool, but not too cold either. Do you have true waterproof pack cover and waterproof bags in there for your clothes instead of what most folks have, trash bags. Trash bags the thick black type are good for a packliner though. Is this what you were using the 16L bag for? Thin trash bags for little garbage buckets are porous I have found and rip very very easily.
And a 40 degree sleeping bag even wearing your parka inside won't be sufficient for summer when it turns nasty out. Generally in summer its fine, but you don't plan for generally average 70 degree or higher days. Even with ALL of your listed clothes on said bag will be good down to at best 20 degrees. I have hiked in plenty of fall days or early spring where max temp was around 20-30 degrees max. Get a 20 degree bag OR, conversely VB socks with down booties and a down coat. This would get your setup down to around late Fallish/Early spring temps. Though definetely still NOT 3+ seasons. Not sure about your shelter and snow... Pans? It WILL snow in the Spring and FALL. In fact a large percentage of our snowpack arrives in the SPRING. Generally not in the fall so much though. Though getting a food dump or more is not uncommon in the fall.