Customising a backpack doesn't necessarily mean stitching, cutting and adapting. The addition of removable straps, cases and holders can help to make being on the move less of a stop-start process avoiding the need to swing off your rucksack to access the contents. Insulated water bottle holders, hard shell cases for reading glasses and clip-on hand loops for shoulder straps are all easy ways to maximise comfort and convenience. Storage pouches slipped over the rucksack hip belt are great for stashing snacks, sunscreen, compass, cell phone, binoculars, notebook and pen.
If your rucksack is a model with welded seams, you will pretty confident that its contents will not get wet. Inside your rucksack, a canoe-style dry bag will absolutely ensure total protection from the elements for any gear stowed away inside even if you fall in a stream. If your paranoia knows no bounds, then a waterproof rucksack cover as well that fits snugly over the whole bag could be the answer.
Most of us will take some form of device – camera, cellphone – to record images of our trips. If you are really into photography, then you will know all about protecting your investment with appropriately padded and readily accessible cases. If you just like to take the odd pic, then consider a padded case attached to a rucksack hip belt or shoulder strap and readily available all day. Packed away in the rucksack for safety, it is only likely to see the light of day in the evening that rather limits the record of any trip. If your camera is an ultra-slim type, you might consider just slipping it into a shirt or jacket pocket but make sure it closes securely.