Sony Online Entertainment has a zero tolerance policy when it comes to PlanetSide 2 mods, and the reason isn't all that surprising. As you can probably guess, SOE is worried about cheating, but their anti-cheating rules also declare harmless third-party apps off limits.
In response to this unusually harsh rule, the publisher did offer some insight into their reasoning, posting their explanation on the official PlanetSide 2 forums.
It is vital that you not run software which modifies the Planetside 2 client in any way. If you do this, you are indistinguishable from various hacks that work in the same manner. The result of this is that you will be banned from gameplay and lose your characters/items.
We cannot make exceptions to this. We do understand there are relatively harmless apps that fall in this category, but if we allowed those they would simply be used as a shield excuse by players trying to cheat. This same rule applies to data that Planetside 2 uses for gameplay. Do not modify any of these files or attempt to modify them in memory.
There are some applications that modify the windows or directx environment without changing the client. These may also result in suspensions unless we specifically exempt them and declare them ok to use.
The most simple guidance here is do not use third party programs which change the Planetside 2 gameplay in any way unless it has been specifically cleared by SOE.
The above does not apply to user initiated *.INI changes, those are allowed, although setting your own options incorrectly can result in bugs.
So that's a bit rough, but their reasoning isn't totally unfounded. Later down the line, players will also be able to use Sony's Player Studio to edit their items and weapons, so there is some room for a more customized experience.