Good news, it isn't sending full power to the front wheels all the time already.
You have a solution in search of a problem. And adding something to an already very complex vehicle is probably not the best. I will go out on a sturdy limb here and say nobody has ever done this. And in order for a mechanism that decouples the front drive axles from the hubs to be of any difference, you'd also need some mechanism to decouple the front driveshaft at the transfer case. Which would add in even more work, and you'd probably just need to use a completely different transfer case.
The only reason I could see for this would be for any performance or fuel economy loss associated with spinning the front driveline all the time. However, this is trivial giving the two and a half tons of meat the engine is already pushing around. I don't think you'd notice it all that much.