I was planning to do so, but decided to do it 3.5 instead. But some ideas were
Races: Dumped Half-orc, Dragonborn, Eldarin, and a couple others, called Goliaths Muls and switched their skill bonuses to +4 for endurance
Classes: Sorcs, Bards and Swordmages got to be psionics with no other changes.
Wizards, if they preserved took a point of damaqge each round they cast spells.
Wizards, if they defiled destroyed one square per casting and could not cast there again. (yes, it would be a pain to mark). But htey got a +2 to hit and damage for it.
Clerics chose an element and all radiant powers did that element instead. Turn undead did half damage to all non-un dead inthe effect but the caster (yes more powerful, but also harder to cast from the middle of the group)
Few other class changes.
Was not sure what to do with rituals, but would have restricted them a lot. For example, arcana rituals would have defiled unless some hp or a surge was spent, and fewer classes (like the Bard) would have auto access to them.
Weapons were reskinned to bone or stone, with obsidian the first magical level and metal above that. With fewer magic items, especially hit and damge bonuses(and crits) there would need to be adjustments, but would not be hard to do with a bit of number fudging.
Would have used minimal magical items, except for weapons (metal) and armor (ditto) which would have been treated as standard magical items, but would not have been actually magical.
Some magical items banned (like food/drink ones)
I was trying for minimal changes and I think it would have worked well, overall. Reskinning is very easy.
