I'm only talking about when an exact match has a low Quality score.
I have seen where I have to broad match phrases one is singular and one is plural. The singular is a 7 QS and the plural is a 5QS. Seems to me it is best to just pause the plural and let the singular pick it up.
I understand that your way gives better reporting and gives you more options. I'm just saying at some point when you have done all that you say and you keep getting a 5QS on an exact term and a broad term is at 7QS or better you can just pause the exact term or let the phrase match get it.
Let's say you have an exact of "best purple widgets" that you know converts at 5%. You can bid exact and likely have a lower QS and higher CPC, but you'll get traffic you know converts.
If you tried to use broad or phrase, you'd also get phrases such as "10 best purple widgets" that may convert at a rate of only 1%.
You'll end up getting more traffic for less per click, but overall, you may end up spending more to make less.
Obviously, that's what negatives are for, but it's hard to get every negative.
In the end, sometimes it is better to pay more per click for laser targeted traffic than paying less for marginally targeted traffic.
I am talking about a very specific situation. Some people don't bid down broad matches. They want to rank top 3. They just put in negative keywords to clean it up. I am only talking about a situation where exact match gives a lower QS than the broad match.
In January 08, Google stated that displayed quality score is only based off the exact match variation of the keyword.
As the quality score you see in your account, is not what's actually used to determine the ad rank (due to real time matching) then what you are proposing sounds good, but might not actually work in reality due to that last second real time analysis of keyword to variation.
I generally find that when you have a broad matched word that's doing great, there are a few variations where it does well, and other variations where it doesn't do well. In Google's system, that keyword could look like it has a high QS, yet on the words where it's not doing well, it actually doesn't have a good QS.
Ok - posting before finishing first cup of coffee - hope that makes sense. If not - then I'll clarify :)