how about twin charging a 2.5gt? supercharger and turbo, it will require custom work, but you wont have to worry about a small turbo to spool, just the instant supercharger (no lag) and a big turbo. dont know about the room in the engine compartment, and how the intercooler would hook up.
supercharger to turbo to intercooler to engine?
supercharger to engine(not intercooler, or watercooled intercooler??), and turbo to intercooler to engine?
this would be interesting to see, i heard they work descent cause no lag, and top end power of the turbo