You are both right an also both wrong...

Yes 175 is a bit heavy... yes 48 HP (as BMW mentioned for the new G650GS) are not too many.
but:
As an 3 year owner of BMW F650ST, I can say that an 650 cc single commuter is quite OK. My 48 HP Beemer had 198 (or so) kg to move (plus me) and managed more than OK in the city traffic (Bucharest has very busy traffic). Mileage was super-OK. 5-6 Liter for 100 km. Now I ride a 900 cc Triumph and it does not get beneath 8 in the city. I can asume that Loncin will do better having fuel injection and less kilos to move.

As the price goes... If it stays inside 5000-6000 Euro limis I think it will do ok (with good dealer support).

IMHO:
1. Loose one of the front disks, save some $$ and weight. one 320 mm disk with one radial Nissin caliper is good enough
2. loose the sci-fi exhaus and put an economical round or oval (arrow-style maybe)