Falling Icicle
Adventurer
As far as I can tell, there is no general rule against magic items stacking without limit. If you have several items that raise AC, saving throws, ability scores, etc., nothing prevents them from all stacking together, raising one's stats to game-breaking levels. This entire problem can be solved with a very simple general rule: magic item bonuses to any particular stat do not stack with each other unless the item explicitly says otherwise. This seems like a pretty obvious and necessary rule to have in the game, and yet I haven't seen any such rule in the playtest packet (please correct me if I'm wrong).
In 2nd edition, bonuses to things like AC didn't stack. Magic armor, barkskin spells, rings of protection etc. did not stack with each other. This kept one's AC within sane limits. In 3e, they added an elaborate keyword system to denote what could stack and what couldn't, but this quickly skyrocketed out of control and was easily abused, especially after the game had been out for a few years and alot of new books offered new ways of getting stacking bonuses. In Next, especially with bounded accuracy, I think the 2nd edition model would be best.
I already know what alot of people are going to say: "but the DM controls the magic items!" While it is true that magic items are under the DM's control, it makes the DM's job alot easier if he doesn't have to worry about giving the players certain combinations of items because they might stack to a point that they break the game. If the DM wants to introduce an item that specifically stacks with other items, he can do so at his own peril. But by having a no-stacking rule by default, DMs can avoid most of the pitfalls without any additional burden being placed on them. IMO, anything that makes the DM's job easier is a good thing!
There's also a less obvious benefit to this approach. If characters couldn't stack bonuses, they'd only "need" a couple or a few magic items to boost their important stats, and after that, they could spend their attention on seeking out magic items that are actually fun and interesting, rather than just more +X items. The power-gaming mentality would largely be removed from the magic item equation, and I think that would be a good thing!
In 2nd edition, bonuses to things like AC didn't stack. Magic armor, barkskin spells, rings of protection etc. did not stack with each other. This kept one's AC within sane limits. In 3e, they added an elaborate keyword system to denote what could stack and what couldn't, but this quickly skyrocketed out of control and was easily abused, especially after the game had been out for a few years and alot of new books offered new ways of getting stacking bonuses. In Next, especially with bounded accuracy, I think the 2nd edition model would be best.
I already know what alot of people are going to say: "but the DM controls the magic items!" While it is true that magic items are under the DM's control, it makes the DM's job alot easier if he doesn't have to worry about giving the players certain combinations of items because they might stack to a point that they break the game. If the DM wants to introduce an item that specifically stacks with other items, he can do so at his own peril. But by having a no-stacking rule by default, DMs can avoid most of the pitfalls without any additional burden being placed on them. IMO, anything that makes the DM's job easier is a good thing!
There's also a less obvious benefit to this approach. If characters couldn't stack bonuses, they'd only "need" a couple or a few magic items to boost their important stats, and after that, they could spend their attention on seeking out magic items that are actually fun and interesting, rather than just more +X items. The power-gaming mentality would largely be removed from the magic item equation, and I think that would be a good thing!