I dont think they need lighter engines, because if anything the weight raito according to where the engines are are way off (too center ballanced).
I kind of hear what your talking about with the clutchs but I use a button as a clutch and just have to use it like I'm releasing a brake(same with the GTR class). Soo I gotta rev it to 4k let out the clutch, pop the clutch again and get the momentiun going.