Flat 6 naturally aspirated engines are the epitome of Porsche and roadsters.
Putting a turbo and its lag on a short wheelbase, nimble car is like putting ice in your Opus One. A different way to enjoy it but loses the whole point of the thing.
Porsche had a real tough time increasing the power of the flat 6 engine without increasing the costs while at the same time not sacrificing reliability during the warranty period.
They couldn't do all three anymore. So they went with the Volks Wagen approach of using turbo fours. Which is also the Hyundai approach.
You want a fun car? Get a 1999 2.5 Boxster. Instead of using the money for a turbo, Slap some lightweight wheels on it, strip the interior, put in a free flow exhaust, intake and headers and you'll be within a few pounds of the Spec Boxster race cars (~2,500 lbs.) while not being limited to their rules on what you can upgrade.