Why would anyone want a half keyboard for gaming though? Use a normal keyboard.
If you want it for macros - then add a second normal keyboard for 1/2 the price and 3x the amount of keys.
For the same reason people consider TKL keyboards more suitable for gaming - the space between the left and right hand is narrowed down increasing the comfort and performance. Some people even turn the keyboard 60-80 degree to the right to narrow it even further. I've noticed that effect using Razer's Orbweaver but the straight rows and disfunctional spacebar with an uncomfortable hump for a wristwrest it's not so comfy.
Still failing to see how another device on the desk is going to free up space for a mouse. If you're implying people replace their keyboard with that, then I think you overestimate the amount of people who only use their PCs for gaming.