The 4WD model weighs 720 kg while the 2WD model is satisfied with 670 kg. That is good enough, it seems that weight reduction policy combined with better engines will make the RS outclass the current Alto Works we have in the game, it just needs to appear in GT7.
Modern Kei cars have been gaining weight without increase in power, which made them slower than models we used to have since GT2. We haven't received proper sporty Kei models for quite some time, after all.
Additional technical informations for the car can be found here. I also found possible acceleration time for the Turbo RS (2WD, MT), the driver claims around 12.5 seconds. Skip to 0:25 for the actual test: