Venting a tub 6' from any wall, UPC

We have a new bathroom going in (on a new slab). We want to place the tub in the center of the bathroom (6' from any wall that actually meets the ceiling). Our plumber says there is no way to vent it. Any suggestions? Can we increase the size of the vent to meet the horz. requirement.

A 1-1/2" trap arm can go 42"
2" trap arm can go five feet
A 3" trap arm can go six feet from the vent.

Some areas allow for a wet vented fixture over a tub drain, so if you have a lav nearby, you could possibly use that as a "wet vent" for the tub. That may get you your six feet.
Keep in mind though, your plumber has seen your home, we haven't.

Thanks for the info (and for moving the thread to the proper location). I'll mention these suggestions to our plumber.