Sounds complicated for shift-Hing. Never sure which gesture you're on...
How about scripting it? /wave, /finger, /raisehand, ect, so all you have to do is bind an F-key to it (and then you can assign a wheel button to the F-key). I'm not sure all the common gestures used in open-wheeled racing (I saw a video once with an in cockpit camera for a car that looked like the LX series. The purpose (of posting it on the forums) was to show the diffrent wind volume effects in and out of draft, but the drivers as the guy came up behind them kept throwing their arms up. At first, I thought they were trying to tell him to back off their bumper (he was drafting really close), but then I realized it might be a "pass on left/right" signal of some sort...), but I think they should work for all types of cars. Just some wouldn't get noticed quite so much (I'm never really bothered to look in the cockpits of XRRs as I drive past them/they drive past me). But for the LX open configs, for example, it would indeed be nice.
However:
How in the world will this work with the wheel animation without rescripting the whole thing? And how do you decide WHICH side you give the finger to? Back? Left? Right? Front?