John,
From your post:
>waterproof<
>cushioning for a backpack up to 18-20kg (40-44pounds)<
>use in temperatures below 25C (77F)<
>preferably weigh less than 1kg (2.2pounds) per shoe<
From Roger's post:
>> – waterproof<
>Never works. There's this big hole at the top …<
I'll second Roger's point about waterproof shoes. I've bought them, used them and have had buckets of water inside of them. Nothing will keep water out of shoes if the water goes over the top! On my last hike I never went over the tops of my low hikers. It did however rain for 6 hours the first day. Due to a combination of persperation and rainwater running down into the shoes I was walking in full "water buckets". Guess what, these shoes are lined with a well known "waterproof" membrane. Breathable or not, the rate of the water coming in exceeded the rate that it could "breathe" out.
You list cushioning as something you'd like and you reference it to your pack weight. You answer your own question later in your post.
>if anything has to give, it'll be the cushioning (I'll cut the pack weight)<
Cut the pack weight and keep the cushioning. You can have both! BTW I overpronate like a pigeon toed duck with broken ankles and I use low quarter hikers. IMO mid or high top hiking boots do little to control or protect your ankles. I've used and worn both and haven't had an ankle problem yet. (Knock on wood, I feel the pain a comin'.) :-)
Can you exercise and strengthen your ankle?
You're headed in the right direction and that is a good thing for a hiker. :-) You say you would like your shoes to be less than 2.2 lbs per shoe. Trail runners can be had in weights as low as 2.7 lbs per pair! Your choice of shoes/boots is a strictly personal one and I'll not recommend any particular shoe or boot. Shoe choice IMO should be based on comfort, stability, traction and weight. For reference purposes I provide the link below as an example only. Copy and paste it to your address bar and it should take you directly to the correct web page.
http://www.rei.com/product/792620
BTW you may see this link as somewhat humorous as we all seek comfort from our choice of hiking shoes. :-)
What low temperatures due you expect to see while hiking? You mention the upper limit but no lower "extreme". I am a summer hiker. I do not have experience with snow and colder temperatures. I'll defer to anyone else who has first hand experience in these areas.
Good luck and good footing. :-)
Party On ! 2010
Newton