It wouldn't work. Like Pappa said, " There was a time where WWE was getting 6.0 and the WCW 4.0 rating every week."
When WWE purchased WCW, they thought that they could get a 10.0 rating, thinking that they could pull in the WCW audience. Instead, they wound up pulling 3's, because WCW's audience consisted of many people who flipped between the two shows, therefore counting as both their audiences.
A ratings war will never happen unless some other promoter/network team together to put togethern an alternate Monday night show to go against Raw.