I just think that putting the extra weight where it is will make an already poor handling car quite lacklustre to drive. Fine in a straight line on dry roads, but torque + understeer + turbo lag sound like frustration and danger to me in real world driving. Modern FIAT turbo engines that act more like N/A engines are perhaps better, with the TwinAir being right up there as an interesting conversion going forward.
If someone offered me 20HP on a plate with no penalties for the Panda, I wouldn't take it. It would add very little to the driving fun and little to actual performance on a normal road or small track either.
Looking at the other stuff the designer gets up to, I get the impression that he is not interested in all this stuff anyway, he just likes the engineering challenge.