I agree re the syringe, the first time I used it, I really scratched my head, since the end didn't fit into the recessed part of the outflow, the narrow center thing, it was like sawyer had forgotten a piece.
Then I realized you were just supposed to press it against the outside lip, and make the seal manually. That's very bad design, the only thing I do not like on the sawyer to be honest. It's workable, but it's certainly not well designed. A screw in back flush, as you note. or hose tube connection, would be far more efficient, and it would work better.
I'm thinking maybe the fitting for a evernew/platy hose? I'll see if REI has anything like that.
That I think would also remove one of the only legitimate complaints people have about the sawyer, having to carry that syringe on any longer trip, not that it weighs much, but it is something.
Oh, checked, after slapping my head a bit to get it working sort of again.
What is needed is, sadly, two sets of the adaptors, since they are male and female. That will give the required platy/evernew to hose to clean end for backflush. And much more elegant. And leaves two male adaptors, but the problem is then solved, I think I'll do that, it's probably not a good idea to go for more than 4 days with a sawyer without being able to backflush it, just in case.
For me, such things are fine, because I always compare the complexity and weights to what I _was_ carrying, not 0.
I also like one of the guy's here suggestion to use cut out metal coffee filter under gasket on dirty end as a prefilter, sad to waste a metal coffee filter, but the screen would be good for other stuff too.
I have to say, the sawyer is so far the best upgrade I've made, it has better functionality, way better durability, filters what, a thousand times more water than a katadyne? No, if the million gallons is right, it filters 5000 times more. And, by weight, even with adaptors, call it 4oz, it filters around 40,000 times more than aquamira (assuming 3oz for the two bottles, average of 25 gallons treated - rating, 15-30 gallons per set, ie, 8 gallons per ounce total, compared to sawyer's 250k gallons per ounce). And it's fast, it's clean, it's efficient, it's pleasant to use, it has no batteries, it's easy to use. I'm looking for something not to like, and the syringe was it, but once that and the prefilter is resolved, I'd give this the best product of the past few years award.
Man, this amazes me, even dropping the sawyer life rating by an order of magnitude, 10x, that is, you'd need 4000 sets of aquamira to match it. 4000 sets of bottles that will go to land fill, 8000 ounces of industrial chemicals entering your body, 4000 sets of packaging to be tossed into the trash. Ok, I'm convinced. That's not what I call light weight, man, that's hundreds of pounds.