Ah, but here's the rub: If you're going to have to remove the hub to run the tap through it, then are you are going to have to replace the bearings, as previously stated, as they get buggered up when removing the hub? If so, you might as well replace the hub and not bother trying the tap.
I'd suggest you go ahead and use your tap from the outside, with LOTS of cutting fluid and great care. If you end up punching out the first couple threads, not that big of a deal as long as your bolt finds clean threads further in without future cross-threading. Hardened steel has lots of strength, you'll just be losing some margin on that bolt.
Bottom line, I suggest cleaning up the threads with the hub on the car first, just make sure you get every last bit of metal fluff out of the threads afterwards and again, use lots of cutting fluid (oil). The true test of whether this effort is OK is when you put the wheel bolt back in and you can acheive 100 ft. lb torque without stripping. If it strips, then just take a deep breath, let it out, then bite the bullet and purchase a new hub and bearing and consider it a noble effort.
Also, I really would raise holy hell with the last place that touched your wheels....there is absolutely no excuse for stripped wheel bolts and hubs.
On the plains of hesitation bleach the bones of countless millions who at the dawn of victory, sat down to wait, and waiting -- died