The latest Champions Online developer article, this time penned by Brian "Balseraph" Urbanek, discusses 'power replacers'. Power replacers are pretty aptly named as you'll see below:

Power replacers are items you can equip, which will change the effect of specific powers you use in the game. These items are not widely available, and will not be available for every power nor every power set. At launch, Martial Arts and the sets that have something to do with using items will have them. There's talk about letting Sorcery have wands, but it's still a "maybe". The amount of time it takes for us to make and develop power replacers is much longer than the amount of time it takes to create a brand new power, oddly enough. It's our opinion that the majority of players would prefer having a new power than an item that simply makes a cosmetic change to an existing power.

Well, they're not entirely just cosmetic changes. Some do have an in-game effect. For example, Munitions can get a Freeze Ray, which adds a cold snare effect to your gunshots, but the effect is still lower than if you had just taken an Ice power with a snare effect. So, in theory, if you really want to be a Freeze Ray guy, here's a way to do that. It made sense to do it for Munitions and Martial Arts because in many cases it's different kinds of swords or guns and those make too much sense in terms of our customization goals for us not to do them. That being said, we're still investigating and deciding on the payoff of launching a fireball by holding a staff as opposed to just giving you a new power.

Read the rest of the explanation by heading to the link provided above.