There are already a handful of Solstice/Sky 2.4L turbo kits out there, the tuning and installation would be much simpler for the Slingshot.
A turbo might be a bad choice. You're already going to be in danger of snap-oversteer,turbo boost might not be a good idea while trying to not overcome that single rear tire. With low weight that boost is going to come on fast and before you know you'll be heading down the road backwards.
Personally I'll be stripping off the emissions equipment, restrictive exhaust, and seeing what can be done for a better breathing engine. I wonder which version of the 2.4L this will use. Is it direct injected, variable cams? It would be great to install a header, add some cam overlap and pick up another 30-50 horsepower. 220 horsepower while weighing less than 1500 pounds would be ridiculous. A similar power/weight ratio to a ZO6.