Those items certainly help, but they carry limitations as well. You cannot take them into extra-dimensional spaces, so a lot of spells (i.e. rope trick) suddenly become unusable unless you leave your gear behind or if you want to risk some of the problems which come with putting an extra-dimensional space inside of another extra-dimensional space.
As discussed in a
recently resurrected thread, there are no hard-and-fast rules to that effect, except regarding the interactions of bags of holding and portable holes. Expect table variation.
Having scolls (which are paper) and bags all over your body also carries problems of its own in a world where the things you can encounter are capable of setting you on fire.
As a general rule, attended items aren't vulnerable to such effects, unless the character carrying them rolls a 1 on his Reflex save.
Unattended items, however (such as packs abandoned at the start of combat to reduce encumbrance) have no such protection, and the average
Fireball will consume pretty much every non-magical item in your backpack that isn't made of adamantium, so material composition is a relatively minor issue.
A lot of these limitations probably are minor in the grand scheme of things. Still, I'd like to see what a game would look like with a DM that enforces a lot of the things that are usually handwaved away.
I'm imagining Sheldon Cooper rubbing his hands in delight at the prospect. Personally, I can't see it enhancing the experience.
In contrast, I'd also be interested to see what a game would look like with a DM that handwaved rules in favor of a fighter so as to take away some of the perceived limitations to that class. My point being that while I do agree that casters in 3rd Edition do overshadow some of their mundane counterparts, I think that disparity in power is made worse because many groups handwave away many rules, and many of the rules being handwaved are ones that -when absent- benefit casters even more.
I've never seen carrying capacity as affecting casters more than other classes. It affects weak characters more than strong characters, and sure, that means it hits wizards and sorcerers hard - but it affects any other non-Strength-based class just as badly, and Small characters doubly so. Meanwhile, other primary spellcasting classes such as druids and clerics tend towards the brawny, and are not particularly affected.
What rules, in particular, do you consider to affect martial classes specifically that you'd like to see handwaved?