Nice one! - you can ceramic coat the turbine housing and the external wastegate (everything between the exhaust ports/ turbine - to get heat into turbo/ reduce lag) or you could go one step further and do all the hot parts of the exhaust (eg downpipe) to reduce heatsoak (with heat wrap to increase effect/ reduce cost) esp. when waiting on the line before a race

with a vented bonnet (spacers at the back) it can massively reduce underbonnet temps
from what ive read online and what others have done looks like you might have to go for the gt35 to get 600+ hp, as the gt30 would be a bit less (about 500) -or even getting a hybrid specially built - no idea what would be the best for lag and its not my area of expertese and you may be better getting expert advice - MSD?

if you are running an external wastegate you could fit a screamer pipe (noisy, not road legal/ may allow exaust fumes into cabin) but have it silenced (little straight-through silencer!) with its own exhaust, seperate from the main one (thats got to be worth a few Hp) - if it went out the side or back and was quiet enough it could pass an MOT?

I could not find any detailed info on the launch control - is it switchable?/ adjustable?