I do that. Ran a 1/2" air line to a ball valve and coupler on the back of my truck from the supply tank. Turn the high idle on...I can get about 5 seconds out of it before I need to pause with a 3/4 impact. Not ideal...but works with minimal problems.
I also use it for last resort air unloading of tanker trailers.
Investing such money just to be able run tools not really wise. Battery powered impacts much cheaper, working when engine is down. My DeWalt takes lug nuts out in seconds.
The investment was minimal. Maybe $30 total.
I keep a breaker bar if I need to go manual. The air just speeds up the process... my jack also uses air or raises manually... But for me, it still allows me to air offload tanks as a last resort.
It is also allows me to hook up to shop air to keep the truck pressurized while looking for air leaks.
To each his own. It's saved my ass a couple times. Also used the air from that line to *ahem* force fuel back to the primary tank when my levelling valve failed on me in MD once. I try to keep an assortment of useful items in the truck, like hose and hose pinch pliers and plugs, in case these things happen.