That would be awesome. So, plot is Gordon loses his hand/arm. Each HL game seems to have a signature weapon/device. HL1 was the crowbar, HL2-ep2 was the gravity gun so that valve could show off their physics engine. The prosthetic arm could be the new signature device introducing minor RPG elements with Gordon able to replace the prosthetic with what ever tool was required. Whether it be a gravity gun, a crowbar, an ice pick, a hacking tool; you name it.