yes I have wilwoods on my g40 turbo. I'd said they aren't really necessary for road use, they are bloody good though. Normally, when driving a G40, when you get back in a "normal" car you are surprised with how good the brakes are. With the wilwoods it is the other way round they are very good brakes. I use the car for track days and they are well worth it there, on the road I'm not so sure, I'd probably stick with 239mm brakes and some decent quality pads (Ferodo DS2000 or 2500 are good).
if you get hold of an engine that has the g-lader already with it then yeah I do that. If you get an engine with out the supercharger then I'm not sure. On one hand it's good to get it running as close to standard as possible so you can make sure you have a good base to start doing highly customised things such as converting to turbo. But on the other hand, buying a supercharger, running it for a short time and then converting to turbo will be more expensive!