The eternal quest is to make the ISF as light as possible for this exact reason. Lexus make 'lardy' cars, so I can't imagine that will change with this new attempt. It'll have the numbers, look the part, but will need some weight loss to be truly enjoyed, especially if they're trying to put it in the same bracket as the GR Yaris (which it won't match).
Personally I'd love to see Lexus capitalise on their RCF GT win and go down a similar route with the F range, as Toyota have with the GR, but all hope for another decent sporty car from Lexus vanished when they went all SUV in Europe, bar the sluggish and Titanic sized ES.
I do live in hope though!