I was considering a warforged component that gave 2 additional legs (like something out of Robot Jox) and when I looked around, found the artifact in the ECS: tauric belt. It seems to me somewhat ridiculous that this item is an artifact. Regardless, I want a less powerful version that is more a mechanical upgrade than a magical item.
How about: Quadraped Component - the warforged goes through an artificing process that removes its current biped legs replacing them with a square based quadraped system for a stability bonus (+4 vs. trip, bullrushing, etc.) and +10' movement. That in and of itself seems that it should not be that expensive - perhaps the same price as boots of springing and striding.
However, for flavor, it would make sense to get some additional benefits of a larger size: occupying a larger space, penalty to hit, penalty to AC, getting a boost to size related checks (grappling, bullrushing, etc.), and getting a str boost: +2 or +4.
However, I don't want the ability to use larger weapons, extended reach, or any of the traditional stat boosts (str/con) for increasing in size.
First off, is there anything like this already in existance? If not, what abilities do you think such a mod should have and how much should it cost?