Valesin said:
All good points and I have considered most of them. But won't the spellcasters also be buffing the fighter-types and not just themselves? Making a fighter's weapon magical (or thanks to Greater Magic Weapon uber-magical) is often a better tactic than buffing yourself. You say that spellcasters can mimic almost any magic item for short periods of time; assuming that they are team players and not selfish bastards won't that help everyone equally?
You're assuming they're team players? Well, okay, most mages I've seen are team players, in that they'll co-operate with other PCs in combat, will cast Glitterdust to make the rogue really happy, will rescue a PC in trouble and expect to be rescued if they get into trouble, etc. They just don't buff their team mates - not enough spell slots! When I played a mage, the only buffs I had that I could cast on other PCs were Mage Armor (reserved for myself) and Resist Energy. I didn't have enough spell slots to cast Greater Magic Weapon or stat-boosting spells on anyone else ... and that campaign ended at 11th-level.
I don't think it's selfish to not prepare Greater Magic Weapon and instead prepare Fireball. You can save your party's life with either spell. Note that, when it came to stat-boosting spells, there was little points. Sure the fighter wanted an enhancement bonus to Strength... which is why he had a Strength-boosting item. Removing items would force mage players to think differently, not necessarily a bad thing, but IMO would require giving mages more slots so they can spread the love. That's a big rules change.
A lot of buffing spells like Divine Power are personal-only spells. It gives a Strength boost that would be subsumed by a Strength-boosting item, but that's just not an issue in a low/no item game.
Others, like Mage Armor, are useless to a lot of classes. There's no point of casting it on a ranger who is wearing a chain shirt.
Finally, clerics buff to fight. It's a big part of their power. They'll buff themselves whether there's a fighter around or not. A mage is more likely to cast Greater Magic Weapon on a fighter's weapon, assuming they choose to devote slots to that rather than 3rd-level spells that are more fun for the player of the mage.
Edit: the point about spell damage being unaffected by the lack of items while a fighter's damage is severly hampered is an excellent point. I have been thinking mainly in terms of buffing/utility spells which can be spread around; spells that deal damage are much more powerful by comparison in the low-item world. Thanks for pointing that out.
BTW, make sure you pay attention to saving throw bonuses. It's not just AC getting shafted. While AC gets hit more, saving throws are probably more important over time - well, at least Fort and Will saves.