I ran my Eagle Talon with the O2 sensor safety wired to the side exhaust from 2003-2010 with over 100K miles (HARD racing miles) on it with no issues and no CEL. I drove the car in South Dakota where I bought it from and lived there for 1 year. Then I drove it cross country to California, it sat there for a year while I was overseas (Military). When I got back I drove it to North Dakota and lived there for 1 year. I then drove it back to California and sold it after having it here for 3-4 years. It was always my daily driver, through snow, dirt, racetrack, and on terrible roads. I never once had the rear O2 sensor crap out or throw a CEL or have the car run funny because of the O2 sensor. I really miss that car and I should have never sold it. What you could do BEFORE you remove your cat, is pull the O2 sensor out of the exhaust like I suggested. If it throws a CEL, you could put it back in and reset the ECU. No harm no foul. If I had access to a lift, I would have done this already just for my own info.
2011 Space Grey 135i Manual Coupe Sport
06 GTO , 06 WRX, 59 Bug, 03 SV650