I actually think this is a bad idea. I am personally happy that it's rated R, but I think the box office numbers will suffer hugely.
I think you could've done pretty well with PG-13, since Deadpool is self-aware. Make him mock the stupid PG-13 rating. Curse and have his face obscured and then have him try to rip off the censor box. Have him cut off heads and flowers come out....it could totally be done well.
From a business standpoint you might be right, but I'm happy they are doing it right, which I don't think they could properly do with a PG-13 rating.