The biggest issue I have with 356 style cars on Boxster or 911 donors is the scale.
Old Porsches - 356's, 550's, 718's and early 911's were compact and the dimensions had balance.
As Porsche developed their cars, in order to fit wider tyres to cope with more power the bodies had to be widened, then lengthened and raised both to fit in all the extra stuff a modern car has - ABS, Power Steering, Climate Control, an infotainment
system (whatever the hell that is), etc., and to keep the looks balanced.
Hence, to my eye, a 356 body that's much wider and taller than the originals just doesn't quite work.
Don't get me wrong, I do like the styling of modern Porsches, but they've been designed to look great at the size they are, while the 356 was designed to look good as a tiddler.
To give you an idea of just how bloated a modern Porsche looks compared to the early ones, this is a 550 Spyder parked next to a 'lightweight' Boxster Speedster -
while this is my Spyder (similar size to a 356) next to a modern 911 -
As you can see, the moderns have grown so much that they're now about 25% bigger in every dimension, making them just too big imho.