The G and S flight models ought to be quite similar to the UH-1H, with the G being a comparatively easy model to build since the power train and rotor system are virtually identical, the reflex sight up front is almost the same, and the weapons loads are very similar as well. The Whiskey flies a good deal like a November model Huey, and my impression of the UH-1H from the game is that it's flight model is quite like that of the UH-1N. Therefore, it would seem to follow that tweaking the UH-1H flight model to that of a Whiskey ought to be a reasonable task.
As others have mentioned, the difficulty with the AH-1S and AH-1W compared to an AH-1G is the increased amount of avionics/weapons controls. As for those who like the Z, the AH-1W is just as capable as the current iteration of the AH-1Z (more capable in some respects), and having flown both (1100 hours in the W, 300 in the Zulu), I much prefer the AH-1W. The AH-1W carries a wider variety of ordnance than any other attack helicopter (try loading Sidewinders , TOW, or 5" rockets on an Apache...), so there is a lot of potential there. Plus, on the Whiskey you don't have to scroll through a bunch of MFD pages to access information, it's all right in front of you. Steam gauges have their advantages, you know....