No bueno. Motor needs some back pressure. Plus removing the exhaust just looks silly.
I am aware of one who painted steel rounds and JB-Welded them over the drilled holes as a repair. I don't know if it sounded stock again, he changed the pipes to Rinehart's before I heard it.There are people that drillbit the end holes to widen them. I wouldn't. If you hate the sound replacing those pipes are friggin expensive. I just bought Torqmasters.
It won't really hurt the bike due to the location of the O2 sensor.
But there are better options than drilling the stock pipes potentially ruining them. Just depends if you're willing to spend the money.
There are some slip on options if you really look.
You can shorten any aftermarket F6B pipe. Some say they don't line up but they do. Guys have done it.
Another thing you can do is decat the bike. Which is actually not that expensive.