Lets see,
Effects of wrong offset on the rear for a fwd car.
Lets compile a long list so this bloke cannot justify himself and keep on going about how he wants this SO badly.
Ill start the list-
1. wheels will stick out past your guard, if your car is lowered AT ALL, the body of your car will be resting on the top of your tyre. To correct this problem (depending on the offset of ur vechile and the whell to see if its even possible), you'll have to get the guards rolled.
2. If your wheel/tyre comes past your guard(sticks out) it is illegal in NSW (don't know in other states).
3.having wheels with wrong offset, will mean bye-bye to U turns, and in ur case prob 3 point turns and round abouts. I hope you(and other drivers) have patience because your going to be doing about 10point turns to turn around.

those are the 3 i came up with. Thats basically 3 reasons for you NOT to do this. I am sure people will add to this list, just so you can see even more reasons to justify why ppl are telling you not to do this.